The Moenkopi Formation is a geological formation, spread across the U. S. states of New Mexico, northern Arizona, southeastern California, eastern Utah and western Colorado. This unit is considered to be a group in Arizona. Part of the Colorado Plateau and Basin and Range, this red sandstone was laid down in the Lower Triassic and part of the Middle Triassic, around 240 million years ago. There is no designated type locality for this formation, it was named for a development at the mouth of Moencopie Wash in the Grand Canyon area by Ward in 1901. In 1917 a'substitute' type locality was located by Gregory in the wall of the Little Colorado Canyon, about 5 miles below Tanner Crossing in Coconino County, Arizona. While in the Great Basin and Reeside characterized and named the Rock Canyon Conglomerate, Virgin Limestone, Shnabkaib Shale members in 1921. Salt Creek and the Holbrook Member were found and named in the Black Mesa basin by Hager in 1922; the Sinbad Limestone Member was named in the Paradox Basin by Gilluly and Reeside in 1928.
Gregory named the Timpoweap Member in the Plateau sedimentary province in 1948. The Wupatki Member was first used in the Plateau sedimentary province and its age was modified to Early and Middle Triassic by McKee in 1951. Contacts were revised by Robeck in 1956 and Cooley in 1958; the Tenderfoot, Ali Baba and Pariott Members were named in the Piceance and Uinta Basins by Shoemaker and Newman in 1959. The Hoskinnini Member was assigned in the Black Mesa and Paradox basins by Stewart in 1959. Contacts were revised again by Schell and Yochelson in 1966. Blakey named the Black Dragon and Moody Canyon members in the Paradox Basin and Plateau sedimentary province in 1974. Contacts were revised yet again by Welsh and others in 1979. Kietzke modified the age to Early and Middle Triassic using biostratigraphic dating in 1988; the Anton Chico Member was assigned in the Palo Duro Basin and areal limits set by Lucas and Hunt in 1989. In 1991 areal limits were set again by Hayden. An overview was completed by Lucas in 1991, Sprinkel in 1994, Hintze and Axen in 1995 and Huntoon and others.
Members: Ali Baba Member Anton Chico Member Black Dragon Member Holbrook Sandstone Member Hoskinnini Member or Hoskinnini Tongue Moody Canyon Member Moqui Member Pariott Member Rock Canyon Conglomerate Member Sinbad Limestone Member Sewemup Member Shnabkaib Member Tenderfoot Member Timpoweap Member Torrey Member Virgin Limestone Member Winslow Member Wupatki Member Found in these geologic locations: Black Mesa Basin* Great Basin province* Green River Basin* Las Vegas-Raton Basin Orogrande Basin Palo Duro Basin Paradox Basin* Piceance Basin* Plateau sedimentary province* San Juan Basin* Uinta Basin*Found within these parks: Grand Canyon National Park Capitol Reef National Park Zion National Park Monument Valley Navajo Nation Tribal Park Dinosaur National Monument Glen Canyon National Recreation Area Walnut Canyon National Monument Wupatki National Monument A diverse fossil vertebrate fauna has been described from the Moenkopi Formation from the Wupatki Member and Holbrook Member of northern Arizona.
Described basal vertebrates include freshwater hybodont sharks and lungfish. Temnospondyl amphibians are a common component of the fauna. Temnospondyli include Eocyclotosaurus, Quasicyclotosaurus, Wellesaurus and Cosgriffius; the rhynchosaur Ammorhynchus is rare. Anisodontosaurus is an enigmatic reptile only known from a few tooth-bearing jaws; the poposauroid archosaur Arizonasaurus is known from one complete skeleton and a significant amount of other isolated material. Footprints and several fragmentary body fossils are known from dicynodonts; the footprints of Cheirotherium and Rhynchosauroides are common in the Wupatki Member. Geology of the Grand Canyon Sandstone formations of the United States GEOLEX database entry for Moenkopi, USGS Bibliographic References for Moenkopi
The Colorado Plateau known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus centered on the Four Corners region of the southwestern United States. This province covers an area of 336, 700 km2 within western Colorado, northwestern New Mexico and eastern Utah, northern Arizona. About 90% of the area is drained by the Colorado River and its main tributaries: the Green, San Juan, Little Colorado. Most of the remainder of the plateau is drained by its tributaries; the Colorado Plateau is made up of high desert, with scattered areas of forests. In the southwest corner of the Colorado Plateau lies the Grand Canyon of the Colorado River. Much of the Plateau's landscape is related, in both appearance and geologic history, to the Grand Canyon; the nickname "Red Rock Country" suggests the brightly colored rock left bare to the view by dryness and erosion. Domes, fins, river narrows, natural bridges, slot canyons are only some of the additional features typical of the Plateau.
The Colorado Plateau has the greatest concentration of U. S. National Park Service units in the country outside the Washington, DC metropolitan area. Among its nine National Parks are Grand Canyon, Bryce Canyon, Capitol Reef, Arches, Mesa Verde, Petrified Forest. Among its 18 National Monuments are Bears Ears, Rainbow Bridge, Hovenweep, Sunset Crater Volcano, Grand Staircase-Escalante, Natural Bridges, Canyons of the Ancients, Chaco Culture National Historical Park and the Colorado National Monument; this province is bounded by the Rocky Mountains in Colorado, by the Uinta Mountains and Wasatch Mountains branches of the Rockies in northern and central Utah. It is bounded by the Rio Grande Rift, Mogollon Rim and the Basin and Range Province. Isolated ranges of the Southern Rocky Mountains such as the San Juan Mountains in Colorado and the La Sal Mountains in Utah intermix into the central and southern parts of the Colorado Plateau, it is composed of six sections: Uinta Basin Section High Plateaus Section Grand Canyon Section Canyon Lands Section Navajo Section Datil SectionAs the name implies, the High Plateaus Section is, on average, the highest section.
North-south trending normal faults that include the Hurricane, Grand Wash, Paunsaugunt separate the section's component plateaus. This fault pattern is caused by the tensional forces pulling apart the adjacent Basin and Range province to the west, making this section transitional. Occupying the southeast corner of the Colorado Plateau is the Datil Section. Thick sequences of mid-Tertiary to late-Cenozoic-aged lava covers this section. Development of the province has in large part been influenced by structural features in its oldest rocks. Part of the Wasatch Line and its various faults form the western edge of the province. Faults that run parallel to the Wasatch Fault that lies along the Wasatch Range form the boundaries between the plateaus in the High Plateaus Section; the Uinta Basin, Uncompahgre Uplift, the Paradox Basin were created by movement along structural weaknesses in the region's oldest rock. In Utah, the province includes several higher fault-separated plateaus: Awapa Plateau Aquarius Plateau Kaiparowits Plateau Markagunt Plateau Paunsaugunt Plateau Sevier Plateau Fishlake Plateau Pavant Plateau Gunnison Plateau and the Tavaputs Plateau.
Some sources include the Tushar Mountain Plateau as part of the Colorado Plateau, but others do not. The flat-lying sedimentary rock units that make up these plateaus are found in component plateaus that are between 4,900 to 11,000 feet above sea level. A supersequence of these rocks is exposed in the various cliffs and canyons that make up the Grand Staircase. Younger east-west trending escarpments of the Grand Staircase extend north of the Grand Canyon and are named for their color: Chocolate Cliffs, Vermillion Cliffs, White Cliffs, Gray Cliffs, the Pink Cliffs. Within these rocks are abundant mineral resources that include uranium, coal and natural gas. Study of the area's unusually clear geologic history has advanced that science. A rain shadow from the Sierra Nevada far to the west and the many ranges of the Basin and Range means that the Colorado Plateau receives six to sixteen inches of annual precipitation. Higher areas receive more precipitation and are covered in forests of pine and spruce.
Though it can be said that the Plateau centers on the Four Corners, Black Mesa in northern Arizona is much closer to the east-west, north-south midpoint of the Plateau Province. Lying southeast of Glen Canyon and southwest of Monument Valley at the north end of the Hopi Reservation, this remote coal-laden highland has about half of the Colorado Plateau's acreage north of it, half south of it, half west of it, half east of it; the Ancestral Puebloan People lived in the region from 2000 to 700 years ago. A party from Santa Fe led by Fathers Dominguez and Escalante, unsuccessfully seeking an overland route to California, made a five-month out-and-back trip through much of the Plateau in 1776-1777. Despite having lost one arm in the American Civil War, U. S. Army Major and geologist John Wesley Powell explored the area in 1869 and 1872. Using wooden oak boats and small groups of men the Powell Geographic Expedition charted this unknown region of the United States for the federal government. Construction of the Hoover Dam in the 1930s and the Glen Canyon Dam in the 1960s changed the character of the Colorado River.
Reduced sediment load changed its color from reddish brown t
Cross-cutting relationships is a principle of geology that states that the geologic feature which cuts another is the younger of the two features. It is a relative dating technique in geology, it was first developed by Danish geological pioneer Nicholas Steno in Dissertationis prodromus and formulated by James Hutton in Theory of the Earth and embellished upon by Charles Lyell in Principles of Geology. There are several basic types of cross cutting relationships: Structural relationships may be faults or fractures cutting through an older rock. Intrusional relationships occur when an igneous dike is intruded into pre-existing rocks. Stratigraphic relationships may be an erosional surface cuts across older rock layers, geological structures, or other geological features. Sedimentological relationships occur where currents have eroded or scoured older sediment in a local area to produce, for example, a channel filled with sand. Paleontological relationships occur where plant growth produces truncation.
This happens, for example. Geomorphological relationships may occur where a surficial feature, such as a river, flows through a gap in a ridge of rock. In a similar example, an impact crater excavates into a subsurface layer of rock. Cross-cutting relationships may be compound in nature. For example, if a fault were truncated by an unconformity, that unconformity cut by a dike. Based upon such compound cross-cutting relationships it can be seen that the fault is older than the unconformity which in turn is older than the dike. Using such rationale, the sequence of geological events can be better understood. Cross-cutting relationships may be seen cartographically and microscopically. In other words, these relationships have various scales. A cartographic crosscutting relationship might look like, for example, a large fault dissecting the landscape on a large map. Megascopic cross-cutting relationships are features like igneous dikes, as mentioned above, which would be seen on an outcrop or in a limited geographic area.
Microscopic cross-cutting relationships are those that require study by magnification or other close scrutiny. For example, penetration of a fossil shell by the drilling action of a boring organism is an example of such a relationship. Cross-cutting relationships can be used in conjunction with radiometric age dating to effect an age bracket for geological materials that cannot be directly dated by radiometric techniques. For example, if a layer of sediment containing a fossil of interest is bounded on the top and bottom by unconformities, where the lower unconformity truncates dike A and the upper unconformity truncates dike B, this method can be used. A radiometric age date from crystals in dike A will give the maximum age date for the layer in question and crystals from dike B will give us the minimum age date; this provides range of possible ages, for the layer in question. Principle of faunal succession Principle of lateral continuity Principle of original horizontality Cross Cutting. World of Earth Science.
Ed. K. Lee Lerner and Brenda Wilmoth Lerner. Gale Cengage, 2003. Nicolai Stenonis solido intra solidum naturaliter contento dissertationis prodromus... Florentiae: ex typographia sub signo Stellae Hutton, James. Theory of the Earth, 1795 Lyell, Charles. Principles of Geology, 1830
Plate tectonics is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, since tectonic processes began on Earth between 3 and 3.5 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century; the geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s. The lithosphere, the rigid outermost shell of a planet, is broken into tectonic plates; the Earth's lithosphere is composed of many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, oceanic trench formation occur along these plate boundaries; the relative movement of the plates ranges from zero to 100 mm annually. Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust.
Along convergent boundaries, subduction, or one plate moving under another, carries the lower one down into the mantle. In this way, the total surface of the lithosphere remains the same; this prediction of plate tectonics is referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual expansion of the globe. Tectonic plates are able to move because the Earth's lithosphere has greater mechanical strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography and density changes in the crust. At subduction zones the cold, dense crust is "pulled" or sinks down into the mantle over the downward convecting limb of a mantle cell. Another explanation lies in the different forces generated by tidal forces of the Moon; the relative importance of each of these factors and their relationship to each other is unclear, still the subject of much debate.
The outer layers of the Earth are divided into the asthenosphere. The division is based on differences in mechanical properties and in the method for the transfer of heat; the lithosphere is more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient; this division should not be confused with the chemical subdivision of these same layers into the mantle and the crust: a given piece of mantle may be part of the lithosphere or the asthenosphere at different times depending on its temperature and pressure. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like asthenosphere. Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year; the driving mechanism behind this movement is described below. Tectonic lithosphere plates consist of lithospheric mantle overlain by one or two types of crustal material: oceanic crust and continental crust.
Average oceanic lithosphere is 100 km thick. Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it was formed. For a typical distance that oceanic lithosphere must travel before being subducted, the thickness varies from about 6 km thick at mid-ocean ridges to greater than 100 km at subduction zones. Continental lithosphere is about 200 km thick, though this varies between basins, mountain ranges, stable cratonic interiors of continents; the location where two plates meet is called a plate boundary. Plate boundaries are associated with geological events such as earthquakes and the creation of topographic features such as mountains, mid-ocean ridges, oceanic trenches; the majority of the world's active volcanoes occur along plate boundaries, with the Pacific Plate's Ring of Fire being the most active and known today. These boundaries are discussed in further detail below; some volcanoes occur in the interiors of plates, these have been variously attributed to internal plate deformation and to mantle plumes.
As explained above, tectonic plates may include continental crust or oceanic crust, most plates contain both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans; the distinction between oceanic crust and continental crust is based on their modes of formation. Oceanic crust is fo
Kayenta, Arizona is a settlement in the Navajo reservation. The Kayenta Formation is a geologic layer in the Glen Canyon Group, spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado and Utah; this rock formation is prominent in southeastern Utah, where it is seen in the main attractions of a number of national parks and monuments. These include Zion National Park, Capitol Reef National Park, the San Rafael Swell, Canyonlands National Park; the Kayenta Formation appears as a thinner dark broken layer below Navajo Sandstone and above Wingate Sandstone. Together, these three formations can result in immense vertical cliffs of 2,000 feet or more. Kayenta layers are red to brown in color, forming broken ledges. In most sections that include all three geologic formations of the Glen Canyon group the Kayenta is recognized. At a distance it appears as a dark-red, maroon, or lavender band of thin-bedded material between two thick, cross bedded strata of buff, tan, or light-red color.
Its position is generally marked by a topographic break. Its weak beds form a bench or platform developed by stripping the Navajo sandstone back from the face of the Wingate cliffs; the Kayenta is made up of beds of sandstone and limestone, all lenticular, uneven at their tops, discontinuous within short distances. They suggest deposits made by shifting streams of fluctuating volume; the sandstone beds, from less than 1-inch to more than 10 feet thick, are composed of coarse, well-rounded quartz grains cemented by lime and iron. The thicker beds are indefinitely cross bedded; the shales are fine-grained thin sandstones that include lime concretions and balls of consolidated mud. The limestone appears as solid gray-blue beds, a few inches to a few feet thick, as lenses of limestone conglomerate. Most of the limestone lenses are less than 25 feet long, but two were traced for nearly 500 feet and one for 1,650 feet. Viewed as a whole, the Kayenta is distinguished from the geologic formations above and below it.
It is unlike them in composition, manner of bedding, sedimentary history. The conditions of sedimentation changed in passing from the Wingate Sandstone formation to the Kayenta and from the Kayenta to the Navajo sandstone, but the nature and regional significance of the changes have not been determined. In some measured sections the transition from Wingate to Kayenta is gradual, but in many sections the contact between the two formations is unconformable. In Moqui Canyon near Red Cone Spring nearly 10 feet of Kayenta limestone conglomerate rests in a long meandering valley cut in Wingate; the contact between the Kayenta and the Navajo in places seems to be gradational, but a thin jumbled mass of sandstone and shales, chunks of shale and limestone, mud balls, concretions of lime and iron, lies at the base of the fine-grained, cross bedded Navajo. Mud cracks, a few ripple marks, incipient drainage channels were observed in the topmost bed of the Kayenta on Red Rock Plateau; these features indicate that, in places at least, the Wingate and Kayenta were exposed to erosion before their overlying geologic formations were deposited, are it may be that the range in thickness of the Kayenta thus in part accounted for.
The red and mauve Kayenta siltstones and sandstones that form the slopes at base of the Navajo Sandstone cliffs record the record of low to moderate energy streams. Poole has shown that the streams still flowed toward the east depositing from 150 to 210 m of sediment here; the sedimentary structures showing the channel and flood plain deposits of streams are well exposed on switchbacks below the tunnel in Pine Creek Canyon. In the southeastern part of Zion National Park a stratum of cross bedded sandstone is found halfway between the top and bottom of the Kayenta Formation, it is a "tongue" of sandstone that merges with the Navajo formation east of Kanab, it shows that desert conditions occurred in this area during Kayenta time. This tongue is the ledge that shades the lower portion of the Emerald Pool Trail, it is properly called Navajo, not Kayenta. Fossil mudcracks attest to occasional seasonal climate, thin limestones and fossilized trails of aquatic snails or worms mark the existence of ponds and lakes.
The most interesting fossils, are the dinosaur tracks that are common in Kayenta mudstone. These vary in size, but all seem to be the tracks of three-toed reptiles that walked upright, leaving their tracks in the muds on the flood plains. So far no bone materials have been found in Washington County that would enable more specific identification. During Kayenta time Zion was situated in a climatic belt like that of Senegal with rainy summers and dry winters at the southern edge of a great desert; the influence of the desert was about to predominate, however, as North America drifted northward into the arid desert belt. The Kayenta Formation is 400 feet thick and consists of a fine-grained sandstone interbedded with layers of siltstone; the alternation of these units produces a series of ledges and slopes between the cliffs of the Navajo and Moenave formation
Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geodesy, engineering geology, archaeology and geotechnical engineering; this broad base of interests contributes to many research interests within the field. Earth's surface is modified by a combination of surface processes that shape landscapes, geologic processes that cause tectonic uplift and subsidence, shape the coastal geography. Surface processes comprise the action of water, ice and living things on the surface of the Earth, along with chemical reactions that form soils and alter material properties, the stability and rate of change of topography under the force of gravity, other factors, such as human alteration of the landscape.
Many of these factors are mediated by climate. Geologic processes include the uplift of mountain ranges, the growth of volcanoes, isostatic changes in land surface elevation, the formation of deep sedimentary basins where the surface of the Earth drops and is filled with material eroded from other parts of the landscape; the Earth's surface and its topography therefore are an intersection of climatic and biologic action with geologic processes, or alternatively stated, the intersection of the Earth's lithosphere with its hydrosphere and biosphere. The broad-scale topographies of the Earth illustrate this intersection of surface and subsurface action. Mountain belts are uplifted due to geologic processes. Denudation of these high uplifted regions produces sediment, transported and deposited elsewhere within the landscape or off the coast. On progressively smaller scales, similar ideas apply, where individual landforms evolve in response to the balance of additive processes and subtractive processes.
These processes directly affect each other: ice sheets and sediment are all loads that change topography through flexural isostasy. Topography can modify the local climate, for example through orographic precipitation, which in turn modifies the topography by changing the hydrologic regime in which it evolves. Many geomorphologists are interested in the potential for feedbacks between climate and tectonics, mediated by geomorphic processes. In addition to these broad-scale questions, geomorphologists address issues that are more specific and/or more local. Glacial geomorphologists investigate glacial deposits such as moraines and proglacial lakes, as well as glacial erosional features, to build chronologies of both small glaciers and large ice sheets and understand their motions and effects upon the landscape. Fluvial geomorphologists focus on rivers, how they transport sediment, migrate across the landscape, cut into bedrock, respond to environmental and tectonic changes, interact with humans.
Soils geomorphologists investigate soil profiles and chemistry to learn about the history of a particular landscape and understand how climate and rock interact. Other geomorphologists study how hillslopes change. Still others investigate the relationships between geomorphology; because geomorphology is defined to comprise everything related to the surface of the Earth and its modification, it is a broad field with many facets. Geomorphologists use a wide range of techniques in their work; these may include fieldwork and field data collection, the interpretation of remotely sensed data, geochemical analyses, the numerical modelling of the physics of landscapes. Geomorphologists may rely on geochronology, using dating methods to measure the rate of changes to the surface. Terrain measurement techniques are vital to quantitatively describe the form of the Earth's surface, include differential GPS, remotely sensed digital terrain models and laser scanning, to quantify, to generate illustrations and maps.
Practical applications of geomorphology include hazard assessment, river control and stream restoration, coastal protection. Planetary geomorphology studies landforms on other terrestrial planets such as Mars. Indications of effects of wind, glacial, mass wasting, meteor impact and volcanic processes are studied; this effort not only helps better understand the geologic and atmospheric history of those planets but extends geomorphological study of the Earth. Planetary geomorphologists use Earth analogues to aid in their study of surfaces of other planets. Other than some notable exceptions in antiquity, geomorphology is a young science, growing along with interest in other aspects of the earth sciences in the mid-19th century; this section provides a brief outline of some of the major figures and events in its development. The study of landforms and the evolution of the Earth's surface can be dated back to scholars of Classical Greece. Herodotus argued from observations of soils that the Nile delta was growing into the Mediterranean Sea, estimated its age.
Aristotle speculated that due to sediment transport into the sea those seas would fill while the land lowered. He claimed that this would mean that land and water would swap places, whereupon the proc