Paleozoic Strata
4. The Tonto Group (Cambrian)
The Tonto Group consists of three Cambrian-period formations: the Tapeats Sandstone (100-325ft), the Bright Angel Shale (up to 450ft thick), and the Muav Limestone (up to 800+ft thick). All three formations thicken from east to west. In the Grand Canyon area, the lowest member of the Tonto Group, the Tapeats, lies unconformably atop the tilted and beveled surface of GCS. The highly weathered and eroded nature of the underlying GCS, which in places is capped by a 10-50ft thick weathered horizon, suggests prolonged periods of subarial exposure seperating the cessation of Chuar deposition and the beginning of Tonto deposition. By the time the Cambrian seas rose upon the craton, only relatively small hogbacks of Shunimo Quartzite remained of what had once probably been sizable ridges.
All three formations of the Tonto Group, however, grade into one another relatively smoothly, suggesting a relatively continuous period of deposition. Middleton and Elliot write:
"Cambrian deposits in the Grand Canyon and throughout the Rocky Mountains long have been cited as representing a classic transgressive sequence of sandstone, mudstone, and limestone . . . During Early and Middle Cambrian time, a north-south trending shoreline migrated progressively eastward across the craton . . . resulting in deposition of coarse clastics in shallow water areas to the east and finer clastics and carbonates in more offshore areas to the west" (p. 84; see also illustration on p. 85).
The Tonto Group is the lowest group in the Canyon which preserves fossils of complex metazoans. The fauna is dominated by trilobites, 47 species of which have been reported. The most common genera include Olenellus, Antagmus, Zacanthoides, Albertella, Kootenia, Glossopleura, and Bolaspis (Middleton and Elliot, p. 93). Olenellus is found only in Cambrian deposits. Also present are brachiopods (Lingulella, Paterina, Nisusia), primitive molluscs (Conchostraca), one species of 'primitive' echinoderm (Eocrinus), algal structures, two species of gastropod (Hyolithes, Scenella), and some sponge (?) fragments (Chancelloria - common in Cambrian deposits). The specific assemblages of fossils found in the Tonto Group suggest an early to Middle Cambrian age for Tonto deposition. Middleton and Elliot note that the excellent preservation of the Eocrinus speciments in the Bright Angel Shale suggests a quiet water environment, since they would quickly disarticulate if subjected to strong currents.
Numerous bedding planes within the Tonto Group preserve trace fossils and burrows. These look very much like traces being made today in modern ocean sediments by bottom dwelling and burrowing organisms. Since trace assemblages are depth, environment and substrate dependant, trace fossil assemblages in sedimentary formations can often be used in addition to lithologic features to infer depositional environments. For example, vertical and u-shaped burrows made by a variety of organisms (worms, various arthropods, molluscs, echinoderms) are the dominant trace fossil types in modern intertidal and nearshore deposits. The same type of structures (Corophioides) are also the most common trace fossils in shallow-water deposits of the Tapeats Sandstone and the lower Bright Angel Shale. Higher in the Bright Angel Shale, in deeper-water deposits, trace fossil assemblages are dominated by horizontal traces (Palaeophycus, Phycodes, and Teichichnus) made by organisms moving about on the substrate. This too is mirrored in modern subtidal and distal shelf deposits, where horizontal traces made by various benthonic organisms.
Austin (1994, p. 40) has argued that the vertical burrows, Skolithos and Diplocraterion, in the Bright Angel Shale are 'escape traces' left by organisms escaping rapid sedimentation, and thus do not require long time periods to form. However, as Miller and Byer note, most escape traces "are characterized by down-bent laminae around a pooly defined axial zone and thus are readily distinguishable from Skolithos and Diplocraterion" (Molly Fritz Miller and Charles W. Byers, Abundant and Diverse Early Paleozoic infauna indicated by the Stratigraphic Record, Geology, 12, Jan. 1984, p. 40). The authors also note that both spreiten structures within diplocraterion represent both upward and downward movement of the burrower.
Check out on this page, and this page for an illustration of how trace fossil assemblages can provide information about ancient depositional environments. See also Trace Fossils and Sedimentary Structures: The Cambrian Lower Abrigo and Bright Angel Shale at the Arizona Sed Geology and Paleontology Resource.
5. The Temple Butte Formation (Devonian)
The Temple Butte Formation rests atop the Muav Limestone, but is not conformable with it. The Temple Butte Formation occurs as lens-shaped beds, 100-400ft thick, deposited in in a westward-draining system of channels eroded into the top of the Muav Limestone (Beus, p. 111). These channel deposits are thickest towards the west (about 400ft at Iceberg Ridge), and are progressively thinner towards the east (about 100ft at Marble Canyon).
Fossil contents include placoderm plate fragments assigned to Bothreolepsis, massive stromatoporoids, silicified rugose corals, and crinoid fragments. Also present are several species of conodonts, which which allow for correlation with well-dated localities elsewhere in western North America. Conodonts described from a well-studied outcrop in Matkatamiba Canyon include Polygnathus pennatus, P. xylus, and Icriodus subterminus at the base of the section, Pandorinella insita and Spathagnotus gradatus about 20ft above the base, and Polygnathus angustidiscus about 20ft from the top of the formation (Beus, p.115, 116; Elston and Bressler, 1977). The upper 20ft of the TBF at this locality is devoid of fossils.
6. The Redwall Limestone (Mississipian)
The Redwall Limestone is about 500-800ft thick, is visible in almost all areas of the Grand Canyon, and is easily recognizable because of its red stain. The boundary between the Redwall and the Temple Butte is discontinuous. The Temple Butte surface is eroded and has a relief of about 10ft in a lateral distance of 100 - 200ft, and the base of the Redwall contains a conglomerate of angular limestone and dolomite blocks derived from the underlying Temple Butte (Beus, p. 122), indicating that the Temple Butte was lithified before deposition of the Redwall began.
The Redwall is divided into four members: the Whitmore Wash, Thunder Springs, Mooney Falls, and Horseshoe Mesa members. The Whitmore Wash is nearly pure calcium carbonate (98% pure). The Thunder Springs member consists of alternating layers of chert and carbonate. The Mooney Falls member is once again almost totally pure calcium carbonate (99.5%). The Horseshoe Mesa member consists of thinly-bedded carbonate with occasional chert lenses. Beus writes:
"Deposition of the Redwall Limestone sediments occurred in a shallow, epeiric sea that produced a submerged continental shelf across northern Arizona. Deposits formed during two major [west-east] transgressive-regressive pulses, as demonstrated by McKee and Gutschick (1969). Detailed facies analysis by Kent and Rawson (1980) and Bremner (1986) have confirmed and refined this interpretation. The basal part of the Whitmore Wash Member records intitial deposition during the first transgression under nearshore, shallow, subtidal conditions where high-energy currents produced oolitic shoals. As the transgression proceded, more offshore deposits of skeletal grainstone and packstone accumulated under quieter water and more open-marine conditions. The Thunder Springs Member accumulated in increasingly shallow conditions as the sea regressed westward." (p. 128).
Another sequence of transgression-regression is also seen in the upper two members of the Redwall, the Mooney Falls Member and the Horseshoe Mesa Member. Based on fossil assemblages, lithology, and stratigraphic position, the Redwall Limestone is a "correlative of the Escabrosa Limestone of southeastern Arizona, the Leadville Limestone of southwestern Colorado, and the Monte Cristo Group of southeastern Nevada. Four of the five formations in the Monte Cristo Group . . . are nearly identical lithologically and in stratigraphic position with the four members of the Redwall in the Grand Canyon (McKee and Gutschick 1969, p. 14). It is likely that Redwall Limestone deposits were laterally continuous with all the above units at the end of the Mississipian Period" (ibid., 127).
Fossils in the Redwall include some primitive cephalopods, Spiriferid brachiopods, corals (Syringopora is common), crinoids, gastropods, bivalves, blastoids, bryozoans, trilobites and trilobite fragments, conodonts, and some foraminifera. McKee and Gutschick, 1969, pp. 104 & 554, describe several layers of in situ mats of calcerous algae within the Redwall. Each of the four members of the Redwall contain unique conodont microfossils which, along with foraminifera, allow Redwall deposition to be correlated with other formations. A conodont named Gnathodes typicus is found in the Whitmore Wash member and not in the other layers. Scoliognathus anchoralis and Dolignathus latus are unique to the Thunder Springs member. Gnathodus texanus is found in the Mooney Falls member only, and the conodont Taphrognathus variarus is limited to the Horseshoe Mesa member.
7. The Redwall -- Surprise Canyon Boundary
Erosional Features at the Redwall-Surprise Canyon Boundary.
Though only a few million years are thought to seperate the end of Redwall deposition and the begginning of Suprise Canyon deposition, the surface of Redwall Limestone was altered considerably during this time. During this time, a series of westwardly-deepening channels were incised into the surface of the Redwall, up to 400ft thick in some places. Blocky knolls and small erosional "mesas," up to 40ft high, are present on the upper surface of the Redwall, buried by basal Supai sediments. Beus:
"By their nature and distribution, these notches appear to have been a part of a major dendritic drainage system that flowly generally from east to west . . . A preliminary reconstruction of the drainage pattern (Grover 1987) illustrate several major valleys that merge westward. In addition, solution depressions ['sinkholes' - Ed] and caves in the upper Redwall Limestone are filled locally with red mudstone of the Surprise Canyon Formation, indicating the development of a karst topography prior to Surpise Canyon deposition" (p. 132).
This east-west drainage system shows water moving easterly, off of the continent, back into the sea. Paleosols, which require hundreds to thousands of years to form, are also present in some areas on the upper surface of the Redwall (Baars, p. 66). These features are inconsistent with a continuous deep water depositional model. If the deluge theory is true, the entire earth should have been covered with deep water continuously until the end of the 'Mesozoic' (depending on where the flood/post-flood boundary is placed stratigraphically; however, all flood geologists, to my knowledge, classify all paleozoic formations as flood deposits). Secondly, the presence of karst topography with dissolution cavities and paleosols requires prolonged exposure to air and rain, which is again incompatible with the notion that the entire earth was covered with water throughout paleozoic and Mesozoic deposition. Karst topography is forming today in areas where carbonates deposits are exposed to subarial weathering. Strahler (1988) writes:
"Carbonic acid in solution in rainwater enters the ground surface, is enriched in the soil zone, and percolates down to the water table. Moving though various kinds of passageways in limestone strata -- joints and bedding planes -- the acid reacts with the rock surfaces, dissolving the limestone and carrying away the solution products (calcium ions and bicarbonate ions). Flow paths of the groundwater lead to the beds of streams occupying valleys cut slightly below the general level of the water table. In time, a system of open, waterfilled passageways is formed. This system could not have operated under flood waters, which would have been highly turbid and rapidly depositing sediment" (p. 280).
Given the rates of limestone solution via the carbonic acid reaction cited in Strahler (about 60mm per 1000 years), it is evident that flood geology requires a different mechanism, one that can operate underwater (presumably, in carbonate-rich water at that), on time scales of days to weeks.
8. The Surprise Canyon Formation (Mississipian)
The Surprise Canyon Formation occurs as a series of discontinuous lens preserved within channel depressions in the underlying Redwall Limestone. Its thickest section is approximately 400ft. The SCF is divided into three units. The basal unit is composed of primarily of a pebble-to-cobble and local boulder conglomerate displaced from the underlying Redwall (Beus, p. 133). This shows that the underlying Redwall was lithified before the formation of the karst features. The basal unit of the SCF preserves Lepidodendron logs, Calamites, seed ferns, and 22 species of plant spores (Billingsly and McKee 1982, p. 144). Also present are typical nearshore Skolithos and rare Conostichus trace fossils. Unit 2, in contrast, consists skeletal limestone interbedded with thin (3-4cm) beds of quartz sandstone, and preserved an abundance of marine fossils, including corals (Barytchisma, Michelinia, Palaeacis, Amplexus), brachiopods (Composita, and others; see Beus p. 136 for a more complete list), molluscs, bryozoans (Archimedes), foraminifera, conodonts, crinoids and other echinoderms (the blastoid Pentremites, starfish). Trace fossils in this unit are more suggestive of subtidal environment, with horizontal Cruziana-type traces dominant. Unit 3, found only in the western and central Grand Canyon area, consists of dark red-brown to purple laminated siltstone and/or sandstone. In some areas, unit 3 contains oncolitic stromolites.
Beus writes: "Fossil evidence from the spores, foraminifers, condonts, brachiopods, and corals document a latest Mississippian age for the Surprise Canyon Formation. Conodonts indicative of the Adetognathus unicornis Zone occur in the upper part of the middle limestone unit . . . In addition, thin limestone beds in the upper part of unit 3 have yielded conodonts . . . that are indicative of the Rhacistognathus primus Zone of possible earliest Pennsylvanian age. . ." (p. 138).
9. The Supai Group and The Hermit Formation (Pennsylvanian to Permian)
Overlying the SCF and the RWL is the Supai Group(SG). In the western Grand Canyon area, the SG is of predominantly marine origin, whereas in the eastern and central Grand Canyon these strata grade into shallow marine and terrestrial facies. The SG spans the Pennsylvanian /Permian boundry, and in most areas is unconformable with Hermit Formation above it. The SG is divided into 4 members. Of the 4 members, the 3 lowest are of Pennsylvanian age, and the highest is of Permian age.
The lowest member of the SG is the Watahomigi Formation (100-300ft). Its contact with the underlying Redwall is sharp and unconformable. This formation grades from packstone carbonate to pelletoidal to aphanitic carbonate to a sandy, shallow water facies from west to east. Basal conglomerates derived from the Redwall are present in most exposures. Trails and burrows are present on some exposed bedding planes.
Above the Watahomigi Formation lies the Manakacha Formation (150-300ft). The Manakacha primarily consists of quartz sandstone, with intercalated layers of mudstone. Of special interest within the Manakacha are layers of cross-bedded, reversely graded sandstone laminae referred to as "climbing translatent strata." Blakey writes that "climbing translatent strata are thin laminae, generally less than several millimeters thick, that display reverse grading within each lamina. Each lamina displays the migration record of a single wind ripple (Hunter 1977) and, as such, is a powerful indicator of eolian deposition" (p. 154). While cross-bedded sandstone can and does form subaqeously given the right environment, no marine sandstones are known contain these structures, which can be observed forming today in dune environments, and nowhere else. At least three units within the Manakacha Formation are thought to have been formed by subarial, eolian processes.
Above the Manachka lie the sandstones of the Wescogame Formation (100-200ft). The basal part of the Wescogame contains a conglomerate derived from the underlying Manachka. Parts of this formation preserve tracks, trails and burrows. Small vertebrate tracks in the Wescogame are attributed to an early group of mammal-like pelycosaurs (Anamalopus), and to a small amphibian or early Hylonomus-like reptile (Stenichnus). Note that this is the first evidence of terrestrial vertebrate life in the geologic column discussed in this essay.
Above the Wescogame lies the Esplande sandstone, composed almost entirely of climbing translatent strata and sand-slide structures. Additionally, the Esplande Sandstone contains locally abundant plant fossils, vertebrate trackways, and even evaporite deposits, all of which are strong indications that deep sea flood waters were absent during Esplande deposition. In this case, all the evidence points directly to the same conclusion -- that the Esplande was formed by terrestrial depositional processes, not by raging floodwaters.
Plant fossils in the Supai Group are mostly primitive conifers, including Calamites, Cordiates, annularia, Walchia fronds, Pecopteris ferns, and various plant spores. Animal fossils include Spirorbis annelid worm shells.
The Hermit Formation overlies the Esplande Sandstone. There is a minor erosion surface seperating the Esplande from the Hermit. McKee writes:
The general lack of conglomerate on the erosion surface at the Esplanade-Hermit contact is notable. A small lens of conglomerate, which consists of rounded limestone pebbles, was found in a channel at Bunker Trail and a sequence of limestone and conglomerate, a few feet thick occurs at a place near Thunder River Trail, but elsewhere it is scarce or absent. Possibly the scarcity of conglomerate is the result of the hiatus being so short that the Esplanade did not become lithified prior to Hermit Shale deposition. The Supai Group of Grand Canyon, USGS Prof. Paper, 1173, p. 171.
It consists of, variously, ripple marked sandstone, occasional outcrops of eolian sandstone, carbonate rich lime, and mudstone. Blakely notes that "The bulk of the Hermit in eastern and central portions of the Grand Canyon consists of weak, ledge-forming, silty, faintly ripple laminated sandstone and slope-forming mudstone. Generally, ten to fifteen cyclic alternations of these units are present" (p. 177). These cycles may be related to tectonic or climatic changes, which have produced similar sequences in easily-datable Cenozoic deposits.
Some bedding planes within the Hermit preserve plant material (primarily small ferns and cone-bearing plants), insect wings, and vertebrate tracks. These tracks, ichnogenera Anthicnium and Dromopus, are attributed respectively to a small, salamander-like amphibian and a small lizard-like reptile (Lockley and Hunt, 1995, p. 53). Both tracks types have been described from Permian deposits in Europe also.
10. The Coconino Sandstone (Permian)
The Coconino Sandstone (CS) consists of cross-bedded, well-rounded quartz grains. Most of the laminae are composed of climbing translatent strata and sand-fall strata. These are exactly the features we see in modern desert sand seas, such as the Sahara. Strahler explains:
"[D]esert dunes have distinguishing physical properties that set them apart from all other known forms of well graded sand deposits. The dune surfaces are devoid of plant cover and are formed into great wavelike ridges with sharp crests and steep lee slopes. The sand, usually almost entirely of quartz composition, is extremely well-graded in terms of size. The grains are spherical to a degree of perfection not found in water-transported sands. The grains surfaces are frosted by the force of intergrain impacts in free air, not subject to the cushioning effect that is found in water. Under prevailing strong winds, with dry conditions, the sand is carried up the windward slopes by low leaps and rebounds. Upon reaching the dune crest, the grains are projected into the air to fall in the comparitvie calm of the protected lee slope, where they build up the sand slope to a steeper angle of inclination. This slope is the slip face. At an unstable surface layer under gravity slides down the slip face until stability is resumed. This process, repeated innumerable times, gives the dune an internal structure or long, steep sand laminae. This structure is called dune bedding, or planar lamination" (p. 217).
The CS preserves a large section of the Coconino Sand Sea, or erg, which in Permian times covered parts of Utah, Arizona, New Mexico and Montana. Unlike obviously marine formations, which tend to thicken towards the west (seaward), the CS thins toward the west, and is thickest (about 1000ft) in the central Grand Canyon area. Further, the orientation of dunes and wind-ripple marks within the CS suggest that the Coconino erg was transported by wind from the north, not by water from the west. The sheer size and volume of quartz Coconino sands require an extensive amount of weathering, mechanical breakdown and transport of prexisting rock, which would require far more time than the flood model allows.
The CS also preserves a variety of trace fossils which, like the sediment structure itself, are indicative of subarial deposition processes. For example, some laminae preserve perfectly formed raindrop prints (see figure 6 in Middleton et al, p.194). Also present are a variety of vertebrate (small reptiles, some possibly early mammal-like reptiles) and invertebrate (millipedes, spiders) trackways. Pictures of some of these traces and tracks can be seen here. Hunt and Santucci note:
". . . Coconino tracks fall within three species of Chelichnus [also called Laoporus -- Lockley. ed.] [McKeever and Haubold, 1996]. Chelichnus is characterized by rounded manual and pedal impressions that are of nearly equal size and which exhibit five short, rounded toe impressions (though less than five may be preserved). Trackways have a pace angulation of about 90o and the manual and pedal impressions are close together [McKeever and Haubold, 1996]. The three valid species of Chelichnus are distinguished on the basis of size alone and are presumed to be the tracks of caseid-like animal [e. g. Haubold, 1971]. Chelichnus bucklandi has pedal impression lengths of 10-25 mm, C. duncani of 25-75 mm and C. gigas of 75-125 mm [McKeever and Haubold, 1996]" (Taxonomy and Ichnofacies of Permian Tetrapod Tracks from Grand Canyon National Park, 1998).
Similar trackway assemblages (ichnofaunas) are found in correlative Permian eolian deposits around the world, including the De Chelly Sandstone in Arizona, the Lyons Sandstone in Colorado, the Hopeman, Corncockle and Locharbriggs Sandstone Formations of Scotland, the Cornberger Sandstein of Germany, and the Los Reyunos Formation of Argentina (Hunt and Lucas, 1988a,b). Attempts by McKee, Brady and others to duplicate the tracks of the CS indicate that dry sand would have been necessary to retain the smallest of these trackways, such as those of spiders, to the level of detail they found to possess in the CS. Brady (1939, 1947) showed that modern analogues of the Coconino invertebrate fauna failed to leave any impression in sand which was even slightly moist, but that the same animals left clear impressions in dry sand (p. 185). McKee also performed a detailed study of the Coconino tracks, using a large trough and artificial sand dunes. Experiments with various vertebrates and invertebrates, using different levels of water saturation, confirm Brady's conclusion that many of the Coconino tracks were impressed into dry, loose sand. Others appear to have been impressed upon damp substrates.
The Coconino as a Flood Deposit
While virtually all geologists who have studied the Coconino agree that it is an eolian deposit, creationists have argued that the Coconino dunes may in fact have been subaqeously deposited. An examination of this "evidence" reveals it weakness.
Leonard Brand has argued for a subaqeous origin based on trace fossil morphology (Brand, 1978; Brand and Tang, 1991). Brand points to vertebrate tracks which abruptly change direction, and other tracks which move transversely up the dune faces. Brand interprets these in terms of similar subaqeous tracks made by modern amphibians. Lockley, however, points out that there is no good evidence that these tracks were made by amphibians in the first place, and that more recent ichnological work attributes them to early Caseid reptiles, and that some modern reptiles have been observed running up dunes with an obligue orientation. Lockley (1995) states:
"The weight of biological and paleoenvironmental evidence pertaining to the Coconino sandstone . . . strongly argues against a subaqeous origin for the tracks. There is very little evidence to suggest extensive bodies of water in Coconino deposits. Even those who support the swimming interpretation for Laoporus tracks cannot show conclusively that these vertebrate trackmakers were amphibians or that dry-land explanations must be abandoned" (p. 44).
And in 1999:
" . . . we should state clearly that the evidence for flooding is nonexistent. The protomammal tracks [in the Coconino - ed] are often found in association with with countless trackways of spiders, scorpions, and other desert arthropods that could not have been walking around underwater" (p. 69).
Interestingly enough, Brand (1996) himself wrote in the conclusion of a 1996 paper that: "The data do suggest that the Coconino Sandstone fossil trackways may have been produced in either subaqueous sand or subaerial damp sand" (Variations in salamander trackways resulting from substrate differences. Journal of Paleontology 70, 1004-1010). So, Brand's work, even taken at face value, does not necessarily indicate that the substrate was deposited subaqeously, as flood geologist frequently claim.
Of course, even if Laoporus tracks were interpreted as being impressed into a wet substrate, this would not necessarily indicate that the substrate itself was subaqeously deposited, much less that it was deposited by Noah's Flood! In fact, as we've already seen, the other surface features found in the Coconino -- delicate spider and other invertebrate tracks, raindrop impressions [!], complete lack of marine fossils (brachiopods, radiolarians, hyoliths, etc.) or trace fossils of marine organisms, even though underlying and overlying strata are rich in marine fossils -- argue strongly against this theory. Lockley (1999) notes that "a gentle and subtle mechanism is required, for heavy rains or catastrophic biblical floods would simply wash away delicate tracks of spiders and scorpions. One possibility is dew and the condensing of fog and mist onto track surfaces, as is common in coastal dunes in the present day Namib desert" (p.76).
Indeed, the type and distribution of trace fossils in the Coconino argue strongly against Austin's theory. If you look lower in the Grand Canyon at the Tapeats Sandstone, which IS a shallow marine deposit, you find both (locally abundant) marine fossils *and* marine trace fossils and burrows, for instance the U-shaped burrow diplocraterion, the vertical burrow skolithos, plus several varieties of horizontal trace fossils and trails, including cruziana, which is a trilobite trail. You find none of this in the Coconino, despite the fact that many delicate arthropod trails of spiders and so forth ARE present and fairly common!
The subaqeous sand-wave theory promoted by Austin (1994) is rendered dubious on other sedimentologic grounds as well, which overwhelmingly support the eolian interpretation. For instance, whereas the angles of cross-beds in subarial dunes frequently exceed 25-30 degrees, sand waves possess very low angle cross-beds, deviating from the horizontal by about 1-10 degrees. One of Austin's own sources, Allen, writes:
"We cannot emphasize too strongly that sand waves possess low to mild slopes ... it is clear that the sides of the waves rarely dip more steeply than 10 degress overall and can slope as little as 1 degree ..."
The bedforms are also inconsistent with subaqeous deposition. Middleton et al. (p. 195) write:
The low height-to-wavelength ratio of the wind ripples as measured in plan view exposures of many foresets is consistent with those recorded from modern coastal and inland dunes.
The wind-ripples in the Coconino look just like these -- they are very parallel, as opposed to shallow water ripples which tend to be wavy and bifurcating. See photo in Middleton and Elliot, p. 194.
Cuffey notes:
"Careful examination of modern dunes [such as the Great Sand Dunes, White Sands (Collinson, 1986b), Monahans Sand Hills, Nebraska Sand Hills (Ahl brandt & Fryberger, 1982), or on Padre Island (Brookfield, 1984)] indicates that climbing translatent strata, with coarsening-up laminae and rare foreset laminae, form only by the migration and accretion of low amplitude wind ripples in eolian environments (Hunter, 1977; Kocurek & Dott, 1981). Such strata and ripples are ubiquitous in the [Coconino,] Navajo, Entrada, and similar sandstones (Kocurek & Dott, 1981), contradicting a subaqueous origin. Modern eolian sand dunes exhibit internal cross-bedding that is remarkably similar to that in the Colorado Plateau sandstones" (Ahlbrandt & Fryberger, 1982, p. 19; McKee & Ward, 1983, p. 147; Collinson, 1986b, p. 104).
Ralph Hunter, in his classic 1977 paper on the characterisitics of aeolian dune deposits (Basic Types of Stratification in Small Eolian Dunes, Sedimentology, 24, p. 371), wrote:
"Because eolian climbing-ripple structure is generally so different in appearance from subaqueous climbing-ripple structure, a new terminology has been developed. The name, 'climbing-ripple structure', is proposed for any structure formed by climbing ripples, whether or not ripple-foreset cross-stratification is visible. Climbing-ripple structure is potentially composed of wavy layering parallel to successive rippled depositional surfaces and even layering parallel to the vector of ripple climb. The former, called 'ripple laminae superimposed in rhythm' by McKee and here called 'rippleform lamination', is not present, or at least is not visually detectable, in amny eolian climbing-ripple structures. The latter, formerly called 'pseudobedding', 'climbing-ripple stratification', or 'climbing-ripple pseudo-stratification' , is here called 'climbing translatent stratification.' "
The Coconino covers a huge portion of the southwest. The volume of mature quartz sand found in these deposits is immense. In order to account for the Coconino as a rapidly formed "flood deposit," we must assume that it was transported by extremely fast water currents. But how are delicate tracks to be preserved in the midst of such strong water currents? Even if we assume that the Coconino sands were transported by a succession of discrete current pulses, and that vertebrate trackways were made between pulses, it seems likely that each new set of tracks would be destroyed by each new pulse, with little or no net preservation.
Addendum: 5/12/01. One more Piece of Evidence Against the Sand-Wave Theory. The Coconino Sandstone is generally agree to be correlative with the Cutler Formation in southeast Utah. Recently, in situ root traces have been found there. These roots cross-cut the bedding and therefore grew after the cross-bedded sands were deposited. Shawn Duffy notes:
"The roots occur as casts, molds, and traces staining the surrounding host rock. Most roots are an average of 2.5 to 5 centimeters thick and roughly 30 centimeters long. Several roots were discovered to be over 3 meters in length and exhibit a branching or radiating pattern which suggest connecting either to each other or to a centralized point like a tree trunk. The sandstone within the Cedar Mesa Member is primarily white, however, most localities in which the roots occur display strong pink and brown mottled patterns suggesting a paleosol . . . Taken as a whole, the random orientation, definite spacing, and the cutting across of bedding planes along with the association of mottled patterns strongly suggest that we are dealing with an insitu origin for the roots. This in turn supports the interpretation that the Cedar Mesa Member of the Cutler Formation represents a series of terrestrial dunes containing islands of vegetation similar to today's coastal sabkhas" (Shawn Duffy, Permian Root Traces From Natural Bridges National Monument. NPS Technical Report NPS/NRGRD/GRDTR-98/01).
11. The Toroweap Formation (Permian)
The Toroweap Formation (TF) lies above the CS, and covers an area of approximately 65,000km2. The TF thickens to west, like other marine strata in the Grand Canyon area. McKee divides the TF into three members which, in descending order, are referred to as the Woods Ranch, Brady Canyon and Seligman members. These three members of the TF display dramatic facies changes both laterally and vertically.
The Seligman member (~45ft) consists of evaporite deposits to the west, primarily gypsum/carbonate rythmites only a few mm thick, similar to those in the Permian Castile Basin, which grade towards the east into cross-bedded sandstones essentially indistinguishable from the underlying CS, and containing, like the CS, eolian sedimentary structures such as large-scale cross-bedding, sand-flow deposits, and inversely graded laminae (Turner, p. 215). Some of the carbonate units within the evaporite lithofacies preserve dessication cracks, indicating several periods of subarial exposure during the deposition of the upper and lower members of the TF.
The Brady Canyon member (~280ft), grades from cross-bedded eolian sandstone in the east to sandy dolomite to pellected micrite to skeletal micrite to skeletal limestone moving west. Whereas the upper and lower deposits generally contain few if any fossils, the middle limestone member (Brady Canyon) is fossiliferous. In the west, the Brady Canyon member displays an open-marine fauna (bryozoans, brachiopods, crinoids, rugose corals), but in the east this member grades into a restricted marine fauna of gastropods and bivalve molluscs (Turner, p. 220). This indicates a progressively more shallow depositional environment towards the east.
The Woods Ranch Member (~180ft) consists of repetative sequences of evaporite, carbonate and sandstone, and is similar to the Seligman member. Turner (p. 211) notes that the "evaporite beds, which most often are of gypsum, frequently contain laminae of limestone and dolomite several millimeters thick. The evaporite in these laminated intervals is usually about one cm thick. Evaporite beds occur in sequences characterized by a basal carbonate unit up to 1.5 feet thick, gypsum beds up to 3ft thick, and sandstone beds that generally are 1.5ft thick."
12. The Kaibab Formation (Permian to Triassic)
Atop the evaporite-rich Woods Ranch member of the TF lies the Kaibab Formation (KF). The KF is approximately 3-400ft thick, and thickens to the west. The lower contact with the Toroweap is unconformable. Billingsley notes:
"The regional unconformity between the Toroweap and Kaibab Formations is locally very subtle with erosional relief as much as 3 m (10 ft) and is mostly covered by talus. However, at some locations in the western Grand Canyon and within this map area, the Kaibab Formation fills large bowl-shaped depressions, possibly erosion channels, up to as much as 3 km (2 mi) wide and about 45 m (150 ft) deep. Thus, the Kaibab Formation is thicker in the erosional basins and channels where the Woods Ranch Member of the Toroweap Formation is eroded away" (George Billingsley, USGS, Geologic map of the upper Parashant Canyon and Vicinity, Mohave County, Northwestern Arizona, MAP MF -2343).
The KF is divided into two members: the Fossil Mountain Member and the Harrisburg Member. Laterally, the Kaibab strata grade from thick, open marine fauna in the west (fenestrate and ramose bryozoans, crinoids, solitary corals, productid brachiopods) to thin, restricted marine fauna in the east (molluscan pelycopods such as Schizodus, and some gastropods). Vertically, within the Fossil Mountain Member, there is also a gradation from shallow marine fauna and deeper marine fauna. This indicates that the Kaibab sea slowly transgressed inland during the period of Fossil Mountain deposition, slowly deepening the waters of the Kaibab seaway.
The marine fossils within the KF, especially in the western portion, are often found excellently preserved. Of the Fossil Mountain Member, Hopkins notes that even delicate "fossils are often found whole and unabraded - indicating little or no transport" (p. 238). For instance, large brachiopods are often found fossilized on top of bedding planes in the concave up, or life position, sometimes with delicate spines still attached. These characteristics suggest that many of the brachiopods and sponges found in the FMM are preserved in situ, where they grew, rather than being deposited there after being washed inland by Noah's flood.
The Harrisburg Member, unlike the underlying Fossil Mountain Member, preserves primarily ripple-marked, restricted marine lithofacies. Most of the Harrisburg consists of restricted marine fauna, with occasional layers of more open marine fauna, indicating several short-term, cyclic returns of deeper water within the larger-scale trend towards regression of the Kaibab seaway (p. 244). The Harrisburg Member also contains thick evaporite accumulations, about 280ft thick at Harrisburg Dome.
There is an erosional surface at the contact between the upper Kaibab and the lower member of the overlying Moenkopi Formation. Hopkins writes:
"In northwestern Arizona, southeastern Nevada, and southwestern Utah, discontinuous conglomerate-filled channels and breccia deposits occur between the Kaibab Formation and Timboweap Member of the Moenkopi Formation. Reeside and Bassler (1922) termed these deposits the Rock Canyon conglomerate for a channel 250ft deep and 700ft wide in Rock Canyon, which is north of Antelope Spring, Arizona. At several localities channels of the Rock Canyon conglomerate have scoured completely through the Harrisburg and into the underlying Fossil Mountain member . . . associated features may represent paleokarst depressions" (Grand Canyon Geology, p. 231).
Section II: Mesozoic and Cenozoic Strata of the Colorado Plateau
