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

C. Muscovite As Anderson et al. (2017) have shown, muscovite flakes rapidly deteriorate (within days) with constant eolian action, but can last more than a year with constant aqueous tumbling. Mica was sparse in our investigations of modern ergs and only occurred when a crystalline rock source was nearby. Garzanti et al. (2012, 2015) confirmed our observations that mica degrades rapidly in eolian settings. In their studies they found mica in the shoreline sediments, but it disappeared as it was transported to the Namib erg. The presence of muscovite flakes in nearly every thin section of Coconino that we studied (Fig. 16) strongly argues for an aqueous origin of the deposit (see Borsch et al. 2018 in these proceedings). D. Orthoclase Orthoclase, or K-feldspar, is a fairly common mineral in most Coconino thin sections, comprising about 6-10% of the studied samples (Whitmore et al. 2014). Most surprising were angular K-feldspar grains that were sometimes more angular than the quartz grains that surrounded them (Fig. 17). K-feldspar sand remains angular in aqueous settings (Kuenen 1960; Russell and Taylor 1937; Twenhofel 1945) and only becomes rounded when it is transported by wind (Whitmore and Strom 2017; Garzanti et al. 2012, 2015). Garzanti et al. (2015) found the following sequence of mechanical durability of various mineral species in the Namib erg: garnet > quartz > epidote > volcanic rock fragments > feldspars > opaques > pyroxene > amphibole > sedimentary rock fragments. Whitmore and Strom (2018, these proceedings) showed that angular K-feldspars are not only common in the Coconino but in many other supposed eolian sandstones as well. It is difficult to understand how angular K-feldspars could survive in an eolian environment without becoming rapidly rounded unless there was a nearby fluvial or bedrock source. In the absence of a nearby source for the angular K-feldspar, it strongly favors an aqueous origin for the Coconino. E. Zircons Gehrels et al.’s (2011, p. 197) analysis of zircons within the Coconino indicates that many of them were probably derived from the mid-Proterozoic rocks of eastern North America, or possibly, but less likely, from the Ouachita orogen. They suggest that large rivers and northeasterly trade winds carried the Coconino sand from these areas to where it formed dunes during the final stages of the collision of North America with the African continent. We think the zircon evidence is compelling and does suggest a distant origin for some of the Coconino sand. However, based on the muscovite and angular K-feldspar that we have documented in the formation, Whitmore and Garner ◀ The Coconino Sandstone ▶ 2018 ICC 593 Figure 16. Mica within the Coconino Sandstone (from Whitmore et al. 2014). Most is muscovite, but occasional biotite has been found as well. Small red arrows show the locations of the mica.