The Proceedings of the Eighth International Conference on Creationism (2018)

predicted by theoretical models (e.g., McCave 1971; Allen 1980) and confirmed by the available field data (e.g., Berné et al. 1988, 1991), consists of various forms of cross-stratification (Fig. 48). The most important factors promoting the formation of sand waves appear to be an abundant supply of sand and strong unidirectional or tidal currents (e.g., Terwindt 1971 on the sand waves of the North Sea). Sand waves typically develop where the most prevalent sediment size range is from 0.25 to 0.5 mm (2.0-1.0 ϕ) in diameter, and are absent where mud or silt comprises more than about 10- 15% of the bottom sediment. Most sand waves occur in water less than 100 m deep, although much greater depths are occasionally recorded (e.g., the sand waves in 475-800 m depths in the Barents Sea described by King et al. 2014; Bøe et al. 2015). Morphodynamic models have shown that modern sand waves develop when the main oscillatory tidal current interacts with irregularities of the sea bottom, promoting crestward sediment transport, and they migrate in response to other harmonic components of the tidal flow (Hulscher and Dohmen-Janssen 2005; Besio et al. 2008a, 2008b). We think sand waves explain many features of the Coconino Sandstone that an eolian model does not explain. Sediment size, sorting and cross-bed style in sand waves, among other features, are similar to what is found in the Coconino. Seismic studies have shown that sand waves can have foreset lengths up to 50 m, more than twice the length of observed foresets in the Coconino. The average dip of the cross-bed foresets in the Coconino (based on hundreds of measurements by us and others) is about 20°. Modern eolian dunes have foreset dips at the angle of repose (~33°) and modern sand waves have dips ranging from 1 to 35° with an average of 15°. Ancient cross-beds may become compacted during burial, but our work (theoretical and petrographic) shows this can only account for several degrees of dip decrease in the Coconino. The Coconino reaches a maximum thickness of around 300 m in central Arizona. Modern ergs have average thicknesses about an order of magnitude less than this (Table 3). Sand sheet deposits like the Coconino are not unusual, and many of them have an average thickness many times that of modern ergs. The thickness of the Coconino and many other ancient sand sheets is suggestive of marine depositional processes, where thicker sheets of sand can potentially accumulate. It is a common misconception that the sand grains of the Coconino are well-sorted. Our data shows in many cases that it is poorly sorted or moderately sorted. Subaqueous deposits tend to have a greater mix of grain sizes, like we find in the Coconino. In our studies, we sampled the Coconino widely, both laterally and vertically. Mica grains (mostly muscovite) were found in almost every thin section examined from the Coconino. Our experiments (and others) have shown that mica cannot survive the abrasive eolian environment. Micas are known to be a common accessory mineral in subaqueous sands, but they are not found in modern eolian environments unless they are very close to a felsic igneous or fluvial source. The presence of mica in the Coconino strongly argues for a subaqueous origin. K-feldspar is a common mineral in the Coconino and sometimes shows less rounding than quartz grains of the same size, even though it is a softer mineral. From our studies, we know that K-feldspar can often be rounded in an eolian setting rather quickly (Whitmore and Strom 2017). There are no K-feldspar sources close enough to the Coconino sand sea for it to be supplied via eolian processes and still remain angular. Angular K-feldspars can be better explained via subaqueous depositional processes. Along the northern margin and in the Oak Creek Canyon area (in the southern area of the outcrop) the Coconino interfingers laterally with the marine Toroweap Formation. Often the same happens vertically with Coconino-style cross-beds and lithologies in the Toroweap Formation. In the northern part of the Coconino outcrop, pure dolomite beds are contained within the lower portion of the Coconino. Subaqueous sand waves best explain these interfingering deposits and the presence of dolomite. We have found large dolomite clasts near the center of the Coconino sand sea, too far for them to be carried by wind-borne processes. The presence of dolomite beds, ooids and cement in many areas is suggestive of widespread marine processes, not eolian ones. In our studies of ancient Permian sandstones from around the world, we have found that many of them have similarities to the Coconino. For example, many others also interfinger with marine formations, have marine facies and contain dolomite beds. Sand waves might be a better interpretation for these sandstones too. In most places, the base of the Coconino is in sharp contact with the underlying Hermit Formation. The contact can be traced the length of the Grand Canyon. It is hard to explain the lack of topographic relief on top of the Hermit if this was a terrestrial setting. Flat contacts are more easily explained in a marine environment. Occasionally the Coconino and Hermit display a transitional contact. This is best illustrated along the Tanner Trail in the Grand Canyon. Two, meter- thick beds of Coconino occur in the Hermit before the Coconino proper begins. In the eastern Grand Canyon, Tanner Trail is the only place known where the transitional contact can be studied in detail, but we think we have seen a similar transitional contact high on the cliff faces, viewed from the Colorado River, from several places in the Marble Canyon area. Some authors have also reported a transitional contact in the Parashant Canyon area in the north- central part of the Grand Canyon. A contact of this nature indicates evidence is lacking for a large erosional hiatus between the Hermit and Coconino and this can best be explained in an underwater setting. The Coconino (and other Permian sandstones) are well known for their vertebrate footprints. Studies of the trackways, primarily by Leonard Brand, have shown that their unusual characteristics can best be explained by subaqueous track makers. Conventional ideas demand that the tracks were either made or preserved on wetted dunes (light rain or heavy dew). However, there is no hint of adhesion ripples (produced by wind blowing on damp desert sand). Sand waves and various back eddy currents associated with them can nicely explain the unusual features of these tracks, not found in eolian settings. Certain areas of the Coconino contain extensive invertebrate trails and tracks. The substrates probably had to be wet in order to make and preserve these well-defined traces. However, again there is no hint of adhesion ripples or interdunal deposits in these areas. How could these organisms survive in the middle of an erg without water? A better hypothesis would be that the traces were made underwater. Parabolic recumbent folds are a specific type of penecontempora- Whitmore and Garner ◀ The Coconino Sandstone ▶ 2018 ICC 619