However, the addition of probability isopleths dramatically improved the favourableness and readability of gradational shaded data classification.
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The Lynx Group overlies the Arctomys Formation and the contact is gradational. It is overlain by the Survey Peak Formation and the contact is concordant but abrupt.
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Because they are gradational in nature, the exact angle of the backslope used to define these landforms is arbitrary and can vary in the scientific literature.Fairbridge, RW (1968) Hogback and Flatiron. In RW Fairbridge, ed., pp.
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The Outram is present in the Rocky Mountains of Alberta and British Columbia. Its thickness and shale content increase toward the west. It overlies the Survey Peak Formation and underlies the Skoki Formation. Both contacts are gradational.
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Osburn et al. 2002 The formation crops out in a limited area of the southwestern Jemez Mountains. Maximum thickness is . The formation rests unconformably on the Abo Formation and has a gradational contact with the overlying Abiquiu Formation.
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Grant, J. and P. Schultz. 1990. Gradational epochs on Mars: Evidence from west-northwest of Isidis Basin and Electric. Icarus: 84. 166-195. Many slopes in Eridania contain gullies, which are believed to be caused by flowing water.
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The shale tongues typically have sharp basal contacts and gradational upper contacts. The classification broadly correspondences with the Colorado Group classification of the Great Plains region; as such, various units of the Colorado Group are recognized within the Mancos.
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2009, pp.5-6 Maximum thickness is . The formation rests unconformably on the El Rito Formation and has a gradational contact with the overlying Abiquiu Formation. The transition zone is characterized by chert beds assigned informally to the Pedernal chert.
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Mixed within the tall forest, with sharp boundaries at times, sometimes gradational, the short evergreen sandstone forest is found on shallow or poor soils, such as the thin soils over sandstone rock, pebble layers, or deep sand soil with a thin humus layer.
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The Perdrix Formation overlies the Maligne Formation or, where the Maligne is absent, the Flume Formation. It is conformably overlain by the Mount Hawk Formation and the contact is gradational. Laterally it interfingers with the Peechee Formation and the reefs of the Cairn Formation.
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The Naiset Formation is present in Rocky Mountains of southeastern British Columbia. It unconformably overlies the Gog Group. It is overlain by the Cathedral Formation, and the contact is gradational. Equivalent strata to the east of the Kicking Horse area are assigned to the Mount Whyte Formation.
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The top of the Tunbridge Wells Sand Formation is well defined in the southwest of East Sussex but is gradational elsewhere. In the area north of Brighton and west of Lewes the boundary is marked by a massive sandstone, though this is not seen anywhere else.
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Their plan shape grades from circular/polygonal to oval/elliptical. Their bases are sharp, but the tops are gradational. Commonly the dishes are separated by vertical streaks of massive sand called 'pillars'. These pillars can be small- scale structures (Type A pillars) or large and throughgoing high-discharge structures (Type B pillars).
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The Crowsnest Formation is the uppermost unit of the Blairmore Group. Exposures along the Crowsnest Highway (Highway 3) and the railroad west of Coleman are the type locality. It is underlain by the Ma Butte Formation (also known as the Mill Creek Formation). The contact is gradational, with volcanic fragments becoming progressively more common toward the top of the Ma Butte Formation.
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The Grayling Formation unconformably overlies the Permian Fantasque Formation. It is equivalent to the lower Montney Formation in the subsurface of the Peace River plains and to the Phroso Siltstone Member of the Sulphur Mountain Formation in west-central and southwestern Alberta. Its contact with the overlying Toad Formation is gradational. The Toad Formation is conformably overlain by the Liard Formation.
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In that area, the Dox formation, which is the thickest unit of the Unkar Group, has been subdivided into four members. In ascending order, they are the Escalante Creek, Solomon Temple, Comanche Point, and Ochoa Point members. The contacts between members of the Dox Formation are gradational and are based mainly on topographic expression, the sedimentary depositional environment, and color changes.
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The typical characteristics of the range include low-relief high plains with steep margins and slopes and fault aligned river valleys with deep gorges and waterfalls. Soils in the range change with altitude. At lower levels in forests, texture contrast soils are the norm. In the sub-alpine snow gum areas deep gradational soils with moderate amounts of organic matter are common.
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The Ma Butte Formation is also known as the Mill Creek Formation. It disconformably overlies the Beaver Mines Formation. It is conformably overlain by the Crowsnest Formation in the south and the contact between the two is gradational. It is disconformably overlain by the Blackstone Formation in the north, and it is correlative with the Bow Island Formation to the east.
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These areas, including Hat Creek Valley, are those in the immediate vicinity and downhill from likely eruption sites. Fallout of ash will affect areas downwind at the time of an eruption. Within the hazard zones, relative hazard is gradational, decreasing away from the location of potential vents. After an initial explosive eruption, extrusion of gas- depleted dacite magma commonly forms lava domes.
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These systems are inner and midfan subsystem and the outer fan subsystem. The inner and midfan system contains interbedded thin to medium bedded sandstones and mudstones. Structures that are found in these sandstones include load clasts, micro-faults, slump folds, convolute laminations, dewatering structures, graded bedding, and gradational tops of sandstone beds. Partial Bouma sequences can be found within the subsystem.
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Special Paper no. 489, Geological Society of America, Boulder, Colorado. Within the Unkar Group, the upper contact of the Shinumo Quartzite with the Dox Formation appears to be gradational and is marked by a change in topographic expression and color. The basal of the Dox Formation directly overlying Shinumo Quartzite consists of predominantly dark green to black, fissile, slope-forming shale that contains thin sandstone beds.
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A term typically used by Earth scientists, a sabkha () is a coastal, supratidal mudflat or sandflat in which evaporite-saline minerals accumulate as the result of semiarid to arid climate. Sabkhas are gradational between land and intertidal zone within restricted coastal plains just above normal high-tide level. Within a sabkha, evaporite-saline minerals sediments typically accumulate below the surface of mudflats or sandflats.
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A conformable contact can be abrupt, where the contact separates beds of distinct lithology. Abrupt contacts coincide with bedding planes and represent a change in depositional environment, but with only a minor hiatus in deposition with no significant erosion. A brief hiatus without erosion is known as a diastem. Gradational contacts occur where the change in depositional environment takes place over a longer period of time.
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The escarpment consists primarily of the Manlius Formation at the base, which is overlain by the Coeymans Formation. The Manlius Formation contains stromatoporoids and abundant desiccation features, notably prism cracks. The Coeymans Formation is a more massive limestone, appears bluish in color, and contains corals and brachiopods, notably gypidula coeymansensis. The gradational contact between the Manlius and Coeymans Formations represents a transgression, or rise in sea level.
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It is overlain everywhere by the Abo Formation or its equivalents, with the transition typically gradational, with the base of the Abo placed at the top of the last massive marine limestone bed below the fluvial redbeds typical of the Abo. The transitional zone between the Madera Group and the Abo Formation is sometimes assigned to the Bursum Formation, which is not included in the Madera Group.
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Mäki : Mäen from mäki : mäen 'hill'. Speakers may attempt to inflect native words without gradation or other associated morphophonological alternations, if they are previously unfamiliar with the gradational inflection: e.g. paasi 'monolith' will be often have the unalternating genitive singular paasin rather than alternating paaden (compare native vesi : veden 'water', versus recent loanword vaasi : vaasin 'vase'). The discussion below focuses on gradation as it appears in native vocabulary.
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The Cathedral Formation is present in the southern Canadian Rockies of southwestern Alberta and southeastern British Columbia. It reaches a maximum thickness of about 610 metres (2000 feet) at Mount Stephen. It is in gradational contact with the underlying Mount Whyte and Naiset Formations, and with the overlying Stephen Formation. To the west, the Cathedral Formation terminates abruptly against the shales of the Stephen Formation at the Cathedral escarpment.
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Some of these sandstone beds exhibit well-developed soft- sediment deformation structures. No fossils have been found in the Shinumo Quartzite. The lower and middle parts of the Shinumo Quartzite accumulated in coastal tidal flats and the upper part of it represents the deposits of river deltas. The gradational contact between the Shinumo Quartzite and Dox Formation above indicates a shift from deposition in coastal deltas – to fluvial deposition by a large river system.
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The Gasconadian (Tremadocian) is represented in southern New Mexico and west Texas by the upper part of the Bliss Formation and the Sierrite Limestone which is the lowermost formation of the Lower Ordovician (Canadian) El Paso Group. The Bliss is a near shore, deltaic, and beach sandstone deposit; the lower part spans the Upper Cambrian. The Sierrite Limestone is a shallow water, carbonate shelf deposit. The contact between the two is gradational.
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It resembles the Shinarump Conglomerate and the two formations can be difficult to distinguish where the Salitral Formation is absent. However, the Poleo Formation is finer grained and shows other distinguishing lithological features. The lower contact with the Salitral Formation is sharp and scoured, while the upper contact with the Petrified Forest Formation is gradational. The Poleo Formation has an inverse thickness relationship with the Salitral that suggests the thick sections fill valleys cut into the Salitral.
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The oldest of the three younger plains units is intermediate plains material. It forms planar to gently undulating surfaces and both embays tracts of cratered terrain and fills crater floors. Both upper and lower contacts with other plains units are gradational. These gradations suggest that the assignment of age to plains deposits on Mercury is partly dependent on the relative abundance of superposed secondary craters, whose densities vary widely as a function of nearby source craters.
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The Trujillo Sandstone, channel-deposits, and Cooper Canyon Formation, overbank deposits with minor channel and lacustrine deposits, are separated from the Santa Rosa-Tecovas by an unconformity. In eastern New Mexico, the Redonda Formation overlies the Cooper Canyon Formation. The Redonda has gradational eastward transition into the upper Cooper Canyon Formation. The Santa Rosa-Tecovas sequence has sediments made up of clasts derived from the north, northeast, and east of the Dockum, very similar to clasts found in the lower Chinle.
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The basal contact of the Walcott Member with the overlying Sixtymile Formation is conformable. Typically, the contact between the underlying black shale typical of the Walcott and overlying basal red sandstones of the Sixtymile Formation consists of a interval that is gradational in nature. The transition beds and the basal laminated red sandstone of the Sixtymile Formation lack any fragmental or exotic debris, unlike the overlying strata. These field relations thus indicate that deposition was continuous across the Chuar Group-Sixtymile boundary.
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Her breast is composed of a triangle and a sphere. The faceting of the rest of her body, to some extent, coincides with actual muscular and skeletal features (collar bone, ribcage, pectorals, deltoids, neck tissue). Both of her shoulders are coupled with elements of the background, superimposed, gradational and transparent to varying degrees. Unidentified elements are composed of alternating angular structures, The colors employed by Metzinger are subdued, mixed (either on a palette or directly on the surface), with an overall natural allure.
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Both the lower contact of the formation with the Ritito Conglomerate and the upper contact with the Chama-El Rito Member of the Tesuque Formation are gradational. The transition to the Ritito Conglomerate is characterized by thick chert beds, informally designated the Pedernal chert for outcrops around Cerro Pedernal (). Individual beds in the formation thicken across the Canones fault zone, which separates the Colorado Plateau from the Rio Grande rift. This indicates that the formation was deposited after rifting began within the Rio Grande rift.
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Because the slope of a homoclinal ridge dips in the same direction as the sedimentary strata underlying it, the dip angle of this bedding (Ө) can be calculated by v/h= tan(Ө) where v is equal to the vertical distance and h is equal to the horizontal distance perpendicular to the strike of the beds.Easterbrook, DJ (1999) Surface Processes and Landforms, 2nd ed. Prentice-Hall, Inc, Upper Saddle River, New Jersey. Cuestas, homoclinal ridges, and hogbacks comprise a sequence of landforms that form a gradational continuum.
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The conglomerate exhibits a dm- scale gradational contact with a poorly sorted, fine-to-medium-grained sandstone with abundant lithic and feldspar grains. The sandstone is locally tuffaceous and exhibits, in some exposures, low-angle, dm-thick bedforms that are internally massive and dip perpendicularly to the overall attitude of the Alajuela Formation. Otherwise, the sandstone appears massive and highly bioturbated, containing a lower density of molluscan molds than the underlying conglomerate. Original molluscan shell material and marine vertebrate fossils are present but rare.
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Isis Temple-Cheops Pyramid region (Utah Flats), with Shinumo Quartzite cliffs above orange-red Hakatai Shale, upon Bass Formation. In the eastern part of the Grand Canyon, the contact between the Bass Formation and the overlying Hatakai Shale is typically gradational over an interval of a meter or so. For example, in Red Canyon, the contact consists of an interval in which stromatolitic limestone of the Bass Formation is intimately interbedded with coarse clastic sedimentary rock of the overlying Hakatai Shale. In the eastern part of the Grand Canyon, the contact is sharp, but conformable.
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The Florianópolis Formation is thick in the type oil well, and consists of reddish, fine to coarse-grained sandstones with a clay matrix, reddish micaceous shales and siltstones. These clastic units are thought to represent alluvial environments distributed along the western Brazilian basin margin, along the Santos Hinge Line. These alluvial environments were gradational towards the east, with the shallow marine carbonates of the Guarujá Formation, and further to the open basin with the siltstones of the Itanhaém Formation. Biostratigraphical data and its relations with the Guarujá Formation point towards an Albian age.
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The Atrisco Member is reddish-brown mudstone and sandstone, some thick, mostly found in the subsurface but distinctive on well logs and discernible as a gradational boundary at the type section and as a sharper boundary further north. This is overlain by the Rio Puerco Member. Distinctive red beds of the Santa Ana Member of the Ceja Formation in flank of Santa Ana Mesa, New Mexico, USAThe Santa Ana Mesa Member consists of reddish-brown sandstone and conglomerate conspicuous in the flanks of Santa Ana Mesa. It contains a 7.1 Ma pumice bed.
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It consists of low, closely spaced to scattered hills about 0.3 to across and from tens of meters to a few hundred meters high. The outer boundary of this unit is gradational with the (younger) smooth plains that occur in the same region. A hilly and furrowed terrain is found antipodal to the Caloris basin, probably created by antipodal convergence of intense seismic waves generated by the Caloris impact.Schultz, P.H. and Gault, D.E. (1975) The Moon 12, 159-177. The so-called “Weird Terrain” was formed by the Caloris Basin impact at its antipodal point.
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These alluvial environments were gradational towards the east, with the shallow marine carbonates of the Guarujá Formation, and further to the open basin with the siltstones of the Itanhaém Formation. Biostratigraphical data and its relations with the Guarujá Formation point towards an Albian age. The depositional environment of the Guarujá Formation has been interpreted as a tidal flat, like this present-day example in Oregon, United States. ;Guarujá Formation The Guarujá Formation is thick and consists of oolitic calcarenites, which laterally grade to greyish ochre and brownish grey calcilutites and grey marls.
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Broadhead 2019 The base of the Abo is gradational with the Madera Group, and is usually placed at the first massive marine limestone bed below the fluvial sediments of the Abo. It is overlain by the Yeso Formation, with the base of the Yeso placed at the first massive sandstone bed showing frosted grains and other eolian features. The transition zone between the Madera Group and the Abo Formation is distinctive enough in many locations that it is broken out into its own formation, the Bursum Formation.Kues and Giles 2004, pp.
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The intercrater plains unit is commonly marked by the soft outlines of numerous overlapping secondary craters producing a subdued hummocky texture. It is gradational in places with cratered plains material, which forms flat, densely cratered surfaces similar to pre-Imbrian plains on the Moon (Wilhelms andMcCauley, 1971; Scott, 1972) Although both the cratered and intercrater plains deposits are interpreted to be volcanic, the latter has been highly degraded by repeated impacts over a longer period of time. Much of its surface is probably covered by a relatively thick regolith of reworked impact breccias.
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Bristolia can be separated into two distinct groups: one consisting of B. insolens and B. anteros, the other comprising a gradual spectrum of morphologies including B. mohavensis, B. harringtoni, and B. bristolensis morphotypes. The second group reveals a dynamic morphological trend. From the oldest species B. mohavensis, the lineage undergoes gradational increase in intergenal angle and advancement of the genal spines, progressing through B. harringtoni, culminating in B. bristolensis. Younger specimens show a trend back to more acute intergenal angles and less advanced genal spines typical of B. fragilis.
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The Kangaamiut dike swarm (old spelling: Kangâmiut) is a 2.04 billion year old dike swarm located in the Qeqqata region of western Greenland. The dikes cut Archean orthogneisses and are exposed along approximately of the coast and a similar distance up to the inland ice to the east, covering an area of about . To the north it is bounded by the paleoproterozoic Ikertooq shear zone (old spelling: Ikertôq) while to the south the boundary is gradational with a gradual reduction in the density of dikes. The dike swarm was intruded during a phase of extensional tectonics.
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The formation is wedge-shaped, thick (up to below Lake Erie), and laterally extensive, outcropping from Western New York to Cabot Head. It thins from southeast to northwest at around 0.6 metres per kilometre and has a dip of 3° to the south-southwest. The formation is the topmost Ordovician layer in Southern Ontario and is unconformably overlain by the Lower Silurian rocks of the Cataract Group. At its base it has a conformable gradational contact with underlying beds of the Georgian Bay Formation in Southern Ontario, the Carlsbad Formation near Ottawa, and the Oswego Formation in New York.
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The unit appears to be gradational laterally eastward with plains and terra material, undivided, and vertically with intermediate plains material. The intercrater plains material is probably about the same age as the ejecta blanket around Beethoven basin: both units have a high crater density. That the plains unit is younger than Beethoven may be indicated in some areas where the basin’s ejecta blanket appears to be partly obscured by the overlap or embayment of plains material. Spudis and Prosser (1984) have suggested that Beethoven may possibly be late c3 in age or as old as early c2.
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Ranks are assigned based on subjective dissimilarity, and do not fully reflect the gradational nature of variation within nature. In most cases, higher taxonomic groupings arise further back in time: not because the rate of diversification was higher in the past, but because each subsequent diversification event results in an increase of diversity and thus increases the taxonomic rank assigned by present-day taxonomists. Furthermore, some groups have many described species not because they are more diverse than other species, but because they are more easily sampled and studied than other group. Of these many ranks, the most basic is species.
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955, 1992 with gradational contacts with the Goat Island Member (below) and the Guelph Formation (above). In 1995, the US Geological Survey U.S.G.S. Bulletin 2086 proposed a revised stratigraphy based on studies in the Niagara region. It extended the Lockport to Group status and included, from base to top, the Gasport, Goat Island, Eramosa, and Guelph as Formations within the Lockport Group. In a "reference section" in the Niagara River Gorge, the Eramosa was divided into six "units" recognized throughout the Niagara region, but a shaley lower unit previously named for the Hamilton area (the Vinemount Member) was transferred to the Goat Island Formation.
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The distinction between the Tropic Shale and underlying Dakota is marked by the appearance of marine mudstones. In some localities there is a sharp non conformable contact between the Dakota Formation and Tropic Shale. The contact with the overlying Straight Cliffs is gradational with the distinction between the two units defined as the point where sandstone becomes more abundant than shale. The Tropic Shale has two dominate lithologies, with the lower two thirds of the formation consisting of a bluish gray calcareous mudstone that encompasses eleven ammonoid biozones, and the upper third that is a darker gray and non-calcareous that encompasses only one or two ammonoid biozones.
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It did continue to uphold a role in state rituals and mourning rites for ancestors, up until late imperial times (13th–20th century). Monasteries were given names like "Monastery for Honoring Loyalty [to the State]" and "Monastery for the Glorification of Filial Piety". Neo-Confucianism upheld the principle of "gradational love" (), which argued that good people should develop filial piety for their parents and neighbors first, and only in a later stage develop love for humankind. Although this idea was influenced by Mahāyāna Buddhist doctrine, the principle was eventually used as a criticism against Buddhism, which was seen to disregard filial piety in favor of universal kindness.
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The Buildwas Formation comprises olive-green and grey calcareous mudstones and nodular to lenticular calcareous mudstones and argillaceous limestones with shell fragments present throughout. The basal part of the formation consists of grey-green rubbly mudstones, containing comminuted shell debris and overlies the mottled green, grey and purple mudstones of the Rubery Formation with a thick transition in colour and upward decrease in number of hard siltstone beds. The top of the Buildwas Formation shows a gradational increase in thickness of beds and a number of limestone beds, where it grades into the overlying Barr Limestone Formation. The thickness of the formation ranges from , with the thinnest outcrops occurring near Walsall thickening towards Wenlock Edge.
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Where the Shinarump lies on Moenkopi Formation, the upper Moenkopi beds tend to be bleached. The upper contact of the Shinarump with younger Chinle beds tends to be gradational. The partial geologic sequence is as follows, up to the latest Petrified Forest Member:Blakey and Ranney 2008, pp. 56-86 :Petrified Forest Member, Late Triassic, 215 Ma :Shinarump Conglomerate, 225 Ma :Holbrook Member, Moenkopi, Middle Triassic, 240 Ma :Virgin Limestone Member, Moenkopi, (245-240 Ma) :Timpoweap and Sinbad members of the Moenkopi Formation, Early Triassic, 245 Ma By the end of the Early and Middle Triassic the 'Triassic Seas' of the western ocean edge of the North American continent were retreating northwest with deposition of the Shinarump (225 Ma) and Petrified Forest Member (215 Ma).
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Bloomington, Indiana:Indiana University Press. p. 117. David K. Smith, examining Allosaurus fossils by quarry, found that the Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites. A later study by Smith incorporating Garden Park (Colorado) and Dinosaur National Monument (Utah) specimens found no justification for multiple species based on skeletal variation; skull variation was most common and was gradational, suggesting individual variation was responsible. Further work on size-related variation again found no consistent differences, although the Dry Mesa material tended to clump together on the basis of the astragalus, an ankle bone.
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The erosion of tilted sequences of either stratified sedimentary or igneous rock, homoclines, of alternating resistance to erosion produce distinctive landforms that form a gradational continuum from cuestas through homoclinal ridges to hogbacks. Less resistant beds are preferentially eroded creating valleys that lie between ridges created by the erosion of more resistant beds. For example, the erosion of homoclines consisting of resistant beds of either limestone, sandstone, or both interbedded with weaker, less resistant beds of either shale, siltstone, marl, or combination of them will produce either cuestas, homoclinal ridges, or hogbacks depending on the angle of dip of the strata. The greater the difference in the resistance to erosion, the more pronounced the structural control and relief between valley and ridge crest.
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3.7 billion year old paleosols in Yellowknife Bay, Gale Crater, Mars, from Curiosity Rover Evidence of paleosols on Mars is derived from both in-situ and orbital remote sensing investigations of the Martian surface. In-situ chemical / mineralogical analyses (Mars Science Laboratory) and images (Mastcam, MAHLI) from the Curiosity rover in Gale Crater on Mars have shown similarities with soil horizons and soil structures found on Earth. Morphological evidence includes soil features such as gradational alteration and bedding disruption by dilational cracks and veins, consistent with soluans of desert soils, blocky angular ped structures, sand wedges, a shallow gypsic (By) horizon, and vesicular structure. Structures like those found in Earth's desert soils caused by microbial gas production after rains (vesicular structure) have been recognized on Mars, but definitive evidence of life on Mars has yet to be obtained.
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The base of Interval 3 is marked by a cm-scale gradational contact between an underlying shell lag in Interval 2 and an overlying fine-grained calcareous sandstone with lithics and occasional trough cross-bedding and ripple marks (Unit E). A calcarenite occasionally interbedded with sandy limestone (Unit F) occurs stratigraphically above, separated from the underlying calcareous sandstone by an irregular, erosional contact. Sedimentary structures vary within the calcarenite from trough cross-bedding to wavy bedding to low-angle planar cross-bedding, suggesting substantial changes in flow velocities at the time of deposition. The lithologies in Unit F were originally described by Woodring in 1957 as the Alhajuela Sandstone Member of the Caimito Formation. However, based on the age constraints presented below for the Alajuela Formation, this attribution to the late Oligocene—early Miocene Caimito Formation is no longer supported.
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In Moqui Canyon near Red Cone Spring nearly of Kayenta limestone conglomerate rests in a long meandering valley cut in Wingate. Likewise, the contact between the Kayenta and the Navajo in places seems to be gradational, but generally a thin jumbled mass of sandstone and shales, chunks of shale and limestone, mud balls, and concretions of lime and iron, lies at the base of the fine-grained, cross bedded Navajo. Mud cracks, a few ripple marks, and incipient drainage channels were observed in the topmost bed of the Kayenta on Red Rock Plateau; and in west Glen Canyon, wide sand- filled cracks appear at the horizon. 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 (is) accounted for.
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While not supporting endemism, Fowler and Fowler suggested in 2020 that there would have been a subtle gradational provincialism of chasmoraurines from North to South, with the lineage including Chasmosaurus being more abundant in the North, Kosmoceratops being its southernmost member, while the lineage including Pentaceratops was more abundant in the South. Since the two clades overlapped geographically during the uppermost part of the middle Campanian, the speciation event that led to the two lineages may have been caused by latitudinal vicariance prior to the appearance of the first member of the Chasmosaurus lineage, 77 million years ago. By 76 million years ago, the supposed barrier dividing the lineages must have disappeared, as they coexisted afterwards; the dividing line appears to have been located somewhere between southern Utah and northern Montana. Fowler and Fowler also found that Vagaceratops lived about 76.2 million years ago while Kosmoceratops lived about 76-75.9 million years ago, and did not overlap stratigraphically.
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