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

“dust rims” around some of the grains. We found that the Coconino sand ranges in rounding from 2.5 to 3.4 (Figs. 9 and 10) Overall, the Coconino is more angular than what Goudie and Watson found for modern ergs. Since many observations have shown that rounding happens quickly in eolian settings, it is difficult to understand why the Coconino is not more rounded if the eolian hypothesis for its formation is correct. The grain size of the Coconino ranges from about 3.45 ϕ in northern Arizona to about 2.75 ϕ in central Arizona, with a mean of about 3.0 ϕ (Figs. 5 and 6). This is smaller, but not out of, the range of mean grain sizes from modern dunes calculated from the data of Ahlbrandt (1979) and Whitmore et al. (2014), which is about 2.5 ϕ. Although grain size studies of modern marine sand waves are limited, the mean grain size in those is 0.25 to 0.5 mm (2.0-1.0 ϕ; Garner and Whitmore 2011), which is slightly coarser than the range of sand found in the Coconino. It is interesting to note that downwind grain sizes in modern ergs decrease (Crouvi et al. 2008; Jerolmack and Brzinski 2010; Lancaster 1995; Pye and Tsoar 2009; Smalley and Vita-Finzi 1968; Wright 2001). The cross-bedding in the Coconino indicates an increase of grain size with transport to the south. The Coconino was more poorly sorted in northern Arizona compared to values that we found further to the south (Figs. 7 and 8). When comparing the overall grain size and sorting in the Coconino against modern eolian dunes, the Coconino appears to be somewhat out of range, which may be more consistent with aqueous depositional processes (Fig. 47). Wind tends to sort sand grains much better than water can. We think the grain size sorting in the Coconino is more consistent with an aqueous deposit. B. Dolomite Dolomite occurs in the Coconino as beds, ooids, cement and clasts over a relatively large area (Figs. 11-15). It is far from being a “dash of marine sediment” as some have suggested (Hill et al. 2016, p. 203). Although the formation of dolomite is still one of the biggest geological mysteries, its formation must be a wet chemical process (Lippman 1973) that requires special conditions with high temperatures (>100 °C) and/or high pressures (Arvidson and Mackenzie 1999). It also requires constant water circulation and a steady supply of Mg 2+ and CO 3 2- ions (Morrow 1988). These conditions must all be met in order for the mineral to form, and certainly are not going to occur in a desert on any large scale. The presence of dolomite, in four different forms, in the Coconino strongly argues for aqueous deposition. Whitmore and Garner ◀ The Coconino Sandstone ▶ 2018 ICC 592 Figure 12. Dolomite beds in the Coconino at Andrus Point, Arizona. JHW photo 9412-2008. Figure 13. Dolomite ooids contained within the cross-bedded sands of the Coconino. Figure 14. Dolomite cement within the Coconino. WSC-11 has dolomite cement (brown) and several dolomite clasts (two indicated by red arrows). PB-05 has brown dolomite cement, some of which has been replaced with calcite (red). A dolomite rhomb is indicated by the red arrow. Figure 15. Dolomite clasts within the Coconino Sandstone. Also see Fig. 14. It is important to note that the clasts were transported along with all of the other surrounding grains. The clasts are likely too big to be transported by wind; wind sorts materials better than this.