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

recognized six types of eolian strata: planebed laminae, rippleform laminae, ripple-foreset cross-laminae, climbing translatent strata, grainfall laminae and sand flow cross-strata. The only authors who have commented as to whether these types of laminae are present in the Coconino or not are Middleton et al. (2003). They suggest that most of the laminae within the Coconino are wind-ripple laminae, sand flow cross-strata and minor grainfall laminae (pp. 171, 174). Although more study needs to be completed in this area, it seems to us that the laminae in the Coconino might be better explained as subaqueous sand flow cross-strata (Hunter 1985) or something similar. These types of strata have similarities to eolian sand flow cross-strata in that the dips are fairly constant from the top to the base of the foresets, the cross-strata are generally straight and can have a slight to moderate concave-upward curvature near their toes (p. 887). Additionally, at least in smaller subaqueous dunes, Hunter states that sand flow cross-strata are very wide and have poorly defined lateral edges, whereas eolian sand flows are narrow and have well-defined lateral edges (p. 890). We think this better matches the thicker laminae we see in the Coconino, although more work needs to be done. Rouse (2017) did some preliminary work on tracing laminae in thin sections of Coconino. The laminae are very difficult to trace with certainty even over the 5 cm or so length of a thin section. One possibility that might explain discontinuous laminae is spontaneous sorting of grains as they are deposited during grain avalanche events. Makse et al. (1997, 1998) showed that these processes Whitmore and Garner ◀ The Coconino Sandstone ▶ 2018 ICC 598 Figure 22. (A) The brink of a modern dune showing multiple crescent-shaped avalanche tongues in cross-section, features that are missing in the Coconino and most other ancient cross-bedded sandstones (see Hunter 1981). This photo was taken at the brink of a dune a day after a heavy rain; the side lee side of the dune is to the left. Wind subsequently polished the stoss slope (to the right) exposing the cross-sections of the avalanche tongues. Red pocketknife for scale. Glamis Dunes, California. JHW photo 0139-2015. (B) Multiple avalanche tongues down the lee face of a dune in Great Sand Dunes National Monument, Colorado. Note that some of the avalanche tongues extend all the way to the bottom of the dune. JHW photo 1298-2009. Figure 23. Low amplitude ripples, parallel to dip, that can occasionally be found in the Coconino. This is a slab of float that was oriented so the sun highlighted the ripples a bit better. West side of Chino Point, Arizona. JHW photo 5797-2007.