Abstract at the wave, a photogenic landform on the utaharizona border, modern, southwesterly, sand. A feature which is unique to the navajo sandstone at white pocket is a large scale scour, a channellike unit approximately 65 feet thick and 825 across. Sedimentary rocks are types of rock that are formed by the accumulation or deposition of small particles and subsequent cementation of mineral or organic particles on the floor of oceans or other bodies of water at the earths surface. The environmental significance of softsediment deformation. Lecture notes field trip download course materials. This layer forms buttes along the scenic drive in the island in the sky district, as well as the cliff walls of upper horseshoe canyon around the great gallery.
The abundant concretions found in the navajo sandstone consist of sandstone cemented together by hematite fe 2 o 3, and goethite feooh. The fluid flow causes sand grains to saltate up the stoss upstream side of the bedform and collect at the peak until the angle of repose is reached. Geology of the kayenta and chilchinbito quadrangles navajo. A wacke is a sandstone that contains more than 15% mud silt and clay sized grains sandstones are one of the most common types of sedimentary rocks. In a lithic sandstone, the grains are mostly small rock fragments. At this point, the crest of granular material has grown too large and will be overcome. Like the navajo sandstone, its sediment source was at least partly from the appalachian mountains dickenson and gehrels 2003 directly adjacent to the south and west of the erg lay the erg margin facies of the moenave formation. Dune collapse, softsediment deformation, navajo sandstone, interdune.
Geol201 fluvial processes and sedimentary structures related to fluid flow. Navajo sandstone frequently occurs above the kayenta formation and wingate sandstone all three formations are in the same group. Dixon abstract the kayenta and chilchinbito 15minute quadrangles in northern navajo county, ariz. Pdf diagenetic characteristics of the jurassic navajo. Sedimentary sequences a sequence is a vertical succession of sedimentary structures that represents a change in depositional conditions over a period of time. An earthquakeinduced flash flood event within the early jurassic navajo sandstone, white pocket, vermillion cliffs national monument, arizona deshowitz, marc p. Comparison of a vertical sequence of sedimentary and biogenic structures, grain size distributions, and lithologies suggests a similarity between the altamaha river estuary, georgia, and an outcrop of the navajo sandstone near woodside, utah. Interpretation of these deposits suggests that the navajo erg sand sea was one of the most extensive desert systems ever to have existed in the history of the earth, and probably.
It can be distinguished from adjacent jurassic sandstones by its white to light pink color, meterscale crossbedding, and distinctive rounded weathering the wide range of colors exhibited by the navajo sandstone reflect a long history of alteration by groundwater. The eolian navajo sandstone crops out extensively across. Rowe 2005 seasonal patterns of wind and rain recorded by the navajo sandstone pdf version, 7. Discuss the concept of rounding in sedimentary rocks d. Although dominated by eolian sandstone, there are other types of sedimentary rock in the navajo record and these deposits hold important clues in the reconstruction the navajo paleoecosystem. The early jurassic navajo sandstone, well exposed in portions of utah and arizona, has attracted many students of aeolian. Sedimentary structures sedimentary structures are features formed in sediment by physical or biological processes at the time of, or shortly after deposition.
Strata or beds are layers that differ in color, texture, and composition from rock layers above and below. Lecture notes sedimentary geology earth, atmospheric, and. As seen in the previous lab, the specific rock that forms depends on the source material. In the cottonwood area, located at the northern end of the kaibab uplift, a conjugate normal riedel deformation band shear system developed during the laramide in the uppermost navajo sandstone on the outer arc of the upper hinge zone of the east kaibab monocline. The environmental significance of softsediment deformation structures. Illustrate the common structures and textures in sedimentary rocks. Ripple marks are sedimentary structures which indicates agitation by water current or waves or wind. Ni outcrops and the post depositional destruction of aeolian structures.
This is a singularly unilluminating definition, because it doesnt conjure up in the mind of the uninitiated any of the great variety of interesting and significant geometries that get produced by the physical. Virtually every depositional environment can be distinguished by its characteristic sequence of deposition and sedimentary structures. Mudrocks mudrocks are made of fine grained clasts silt and clay sized. Choose from 338 different sets of sedimentary structures flashcards on quizlet. Interpreting cyclic crossbedding, with an example from the navajo. Pelletal glauconite occurs in a correlate of the navajo, the nugget formation of the wind river basin, indicative of a marine environment.
The sedimentary structures which result are roughly horizontal units composed of inclined layers. Fluid transport processes and sedimentary structures related to fluid flow reynolds number stokes law cross bedding. A sedimentary sequence composed of the permian white rim sandstone of the cutler group, triassic moenkopi and chinle formations, and jurassic wingate sandstone, kayenta formation, and navajo sandstone is exposed within the structure fig. Stratigraphic analysis of the navajo sandstone journal.
Because of the cliff weathering and smooth vertical faces, it is often difficult to see and access sedimentary structures in the wingate sandstone. The navajo sandstone consists of thick layers of crossbedded sandstone formed by windblown sand dunes in a vast ancient desert. Geol201 fluvial processes and sedimentary structures related. Describe the mode of formation of the sedimentary rocks b. Navajo sandstone facies of the san rafael swell dune interdune code grain size sedimentary structures thickness m 0. Abstract an earthquakeinduced flash flood event within.
Stratigraphic analysis of the navajo sandstone geoscienceworld. Pdf tetrapod burrows from the lower jurassic navajo. Pdf northwest of moab, utah, the lower jurassic navajo sandstone contains sedimentary structures we interpret as casts of tetrapod burrows at two. Coloration patterns in the jurassic navajo sandstone of zion national park and vicinity are examined using a. Navajo possesses sedimentary structures, such as current lineation, bioturbation, and large scale contorted bedding characteristic of subaqueous conditions of. It is important to remember that in a desert environment, only a percentage of the geography consists of actively moving sand dunes at any given time. Learn sedimentary structures with free interactive flashcards. Atop the cliffs, navajo sandstone often appears as massive rounded domes and bluffs that are generally white in color.
Navajo sandstone frequently occurs as spectacular cliffs, cuestas, domes, and bluffs rising from the desert floor. The navajo sandstone records deposition from the beginning of the pliensbachian through the midtoarchian ages of the lower jurassic. Wind scour of navajo sandstone at the wave central. Sedimentation is the collective name for processes that cause these particles to settle in place. Sedimentary structures include features like bedding, ripple marks, fossil tracks and trails, and mud cracks.
The iron forming these concretions came from the breakdown of ironbearing silicate minerals by weathering to form iron oxide coatings on other grains. The nature, description, and classification of sediments pdf 1. Latter is useful if working in folded and potentially overturned rocks. Paleohydrologic controls on softsediment deformation in. Sedimentary structures are surficial or internal, megascopic, threedimensional features of sediments or sedimentary rocks pettijohn and potter, 1964. What sedimentary structures provide evidence of the wind blown origin of the navajo sandstone in arches national park. Depositional processes and the navajo sandstone gsa. In the study area the navajo sandstone is almost entirely built up of stacked units of crossbedded eolian sandstones. Fault formation in porous sedimentary rocks at high strain. Intradune deformation would enable deflation of deformation features during the normal course of dune migration, more parsimoniously accounting for. Its stratigraphic column is essentially a working timeline of the environments that existed there over the past 250 million years.
The wingate tends to from very blocky, vertical cliffs, likely related to different grain sizes and cementation compared to the younger overlying navajo sandstone. Aug 01, 2004 a noncreationist interpretation for the navajo sandstone. The navajo sandstone is a formation of the glenn canyon group, and represents an eolian dune system comparable in extent to the modern sahara desert. Zion canyon b lobe and cusp structures along the lower boundary of bleaching suggest. Crossbedding is a very important sedimentary structure to recognize. Sandstone sedimentology and stratigraphy aapg wiki. Softsediment deformation and dune collapse in the navajo.
Whether an arkose, greywacke, sandstone, or limestone, forms depends purely on the material that is being deposited, the. In most of the layers the crossbeds dip down toward the right, implying a consistent wind direction from right to left during deposition. Dec 24, 2019 figure \\pageindex2\ crossbedded jurassic navajo formation aeolian sandstone at zion national park, utah. Jurassic navajo sandstone of southeastern utah, usa. Sedimentary structures and environments sean tvelia introduction not all sedimentary rocks form under the same conditions. Current ripples, their relation to patterns of water and sediment motion, northholland publishing. Wind scour of navajo sandstone at the wave university of. Zion national parks geologic history can be broken down into four main parts. Stratigraphic analysis of the navajo sandstone citeseerx. Appalachian mountain siliciclastics source for navajo sandstone.
Jurassic navajo eolian sandstone, glenn canyon, arizona. Crossbeds formed in streams tend to be on the scale of centimeters to tens of centimeters, while those in aeolian wind deposited sediments can. Geol201 fluvial processes and sedimentary structures. Wind scour of navajo sandstone at the wave central colorado. Navajo sandstone is the youngest, dominant rock layer in canyonlands. Crossbedding is formed by the downstream migration of bedforms such as ripples or dunes in a flowing fluid.
The original depositional layering is tilted, such tilting not being the result of postdepositional deformation. In the early jurassic, the climate of the colorado plateau dried significantly, creating desert conditions over a broad region. Sedimentary structures are the larger, generally threedimensional physical features of sedimentary rocks. This rock formation is particularly prominent in southern utah, where it forms the main attractions of a number of. Lecture notes sedimentary geology earth, atmospheric. Sedimentary rocks can tell us a great deal about the. Through such discussion exploration efforts will be aided.
Stratigraphic evolution of the jurassic navajo sandstone. The table below includes specific environments where various types of sediments are deposited and common rocks, structures, and fossils that aid in deducing the depositional environment from examining a sedimentary rock outcrop. Diagenetic coloration facies and alteration history of the jurassic. Like sand, sandstone may be any color, but the most common. The navajo sandstone is the remnant of an early jurassic pliensbachian. Together, these three formations can result in immense vertical cliffs of 2000 feet or more.
Sandstone is a clastic sedimentary reservoir rock composed of mainly quartz andor feldspars, and typically deposited by relatively highenergy processes, which winnow out much of the fine particle size fraction while transporting and depositing the coarser sandsized particles. It is located in the colorado plateau province of the united states. Current ripple marks, unidirectional ripples, or asymmetrical ripple marks are asymmetrical in profile, with a gentle upcurrent slope and a steeper downcurrent slope. In an eolian environment there are two primary types of deposits. The navajo sandstone was deposited in an eolian environment composed of large sand dunes, similar to portions of the modern sahara desert.
Geology of the kayenta and chilchinbito quadrangles, navajo county, arizona by e. Crossbedding in which national park is the great white water rafting location of cataract canyon located. Downslope coarsening in aeolian grainflows of the navajo. The navajo possesses sedimentary structures, such as current lineation, bioturbation, andlargescale contorted bedding characteristic of subaqueous conditions of deposition. Give an account of sediment erosion and transport c. Rowe 2003 longlived pluvial episodes during deposition of the navajo sandstone pdf version, 1. Navajo sandstone is a geologic formation in the glen canyon group that is spread across the u. It can be distinguished from adjacent jurassic sandstones by its white to light pink color, meterscale crossbedding, and distinctive rounded weathering. The navajo sandstone was deposited in an eolian environment composed of large sand dunes, similar to. Pdf downslope coarsening in aeolian grainflows of the.
In geology, crossbedding, also known as crossstratification, is layering within a stratum and at an angle to the main bedding plane. Diagenetic characteristics of the jurassic navajo sandstone in the covenant oil field, central utah thrust belt article pdf available in aapg bulletin 938. In most of the layers the crossbeds dip down toward the right, implying wind direction from right to left during deposition. The feature is filled in its entirety with homogeneous, white sandstone that does not exhibit obvious sedimentary structures. Crossbedding is bedding that contains angled layers within otherwise horizontal beds, and it forms when sediments are deposited by flowing water or wind. Chapter 3 sedimentary structures mit opencourseware. Abstract an earthquakeinduced flash flood event within the. Central to the formation of these erosional steps are crusts produced by microbes lying just beneath. Brookfieldanatomy of a lower permian aeolian sandstone complex, southern scotland. The wingate sandstone erg a large sand sea originally lay at very low latitude, centered approximately 10 o north of the equator. Sedimentary rock sedimentary rock sedimentary structures.
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