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

the angular beach sands (Garzanti et al. 2012; 2015). Although several authors have suggested that round grains are transported more efficiently and are concentrated by eolian processes due to being able to roll easier than angular grains (Folk 1968; MacCarthy and Huddle 1938; Mattox 1955; Mazzullo et al. 1986; Twenhofel 1945) other authors disagree because dunes can be found that have ranges of rounded particles within them and their roundness does not differ from the surrounding desert floor (Folk 1978; Khalaf and Gharib 1985). The lack of consensus is probably because the movement of various shapes, sphericities and sizes of grains is a complex process and is highly dependent on various velocity conditions (Morris 1957; Thomas 1987). In published discussions of sand dunes and formations that contain an abundance of rounded sand grains (like supermature quartz arenites), the consensus seems to be that textural and compositional maturity is inherited and usually the result of several sedimentary cycles (Dott 2003; Folk 1978). Even though there have been several explanations for how quartz grains become rounded, the most popular and reasonable hypothesis remains eolian abrasion (Dott 2003) that happened in at least in one of the cycles in the history of the sand grains. The previous discussion on rounding has focused on quartz which is, by far, the most common component of most sandstones. Pye and Tsoar (2009, p. 72) claim that K-feldspar rounds faster than quartz because of its lower hardness. Some theoretical, experimental and observational rounding data has been collected on K-feldspar grains. Marsland andWoodruff (1937) demonstrated experimentally that K-feldspar rounds slightly faster than quartz. Dutta et al. (1993) completed both theoretical and experimental work on eolian abrasion of K-feldspar. These authors theoretically calculated what changes K-feldspar would exhibit from ballistic impacts and then tested the hypothesis in a wind tunnel. They concluded that eolian sands tend to be fine-grained and quartz-rich because of the tendency of K-feldspar to break apart and become smaller due to ballistic impacts (causing rounding and smaller grains). They reasoned that this explained the size reduction and enrichment of quartz in eolian sandstones. Whitmore and Strom (2017) studied sand along the Pacific coast that was transported into nearby sand dunes. They found that although the K-feldspar was still somewhat angular in the dunes, it had become statistically significantly more rounded even with transport distances of less than 100 m. Garzanti et al. (2015) found that angular sand of all mineral species changes little from marine and fluvial transport but is only significantly altered by eolian abrasion. They state (p. 991): Aeolian impacts are unable to change sand composition by selectively destroying labile components, but can spectacularly modify the morphology of detrital grains, which may become nearly as well-rounded as perfect spheres… Most detrital minerals are still angular to subangular after ca 2000 km of transport along the Orange River, confirming that fluvial environments are ineffective in rounding sand grains. Roundness changes little in the marine environment even after 300 to 350 km of high-energy littoral transport along the Atlantic shores of the Sperrgebiet. This condition demonstrates that beach action, as any transport in aqueous media, does not have much influence either (Pettijohn 1957) and disproves the long-held idea that beach sand rounds faster than river sand because the grains are rolled back and forth repeatedly (Folk 1980). Instead, rounding does occur rapidly at the transition to the aeolian environment in the southern Coastal Namib, indicating that abrasion is much more effective during sediment transport in air, where grains hit and round faster because of higher density contrast and lack of cushioning effect by the water film. Roundness reaches maximum in the central Coastal Namib and changes little further north, confirming that the rate of wear is greatest in the early stage of wind transport and declines exponentially with distance (Krumbein 1941). From their observations they also concluded the “relative toughness” or susceptibility of various minerals to rounding (p. 992): Based on the observed compositional trends and differential rates of roundness increase with transport distance, the following sequence of relative toughness and mechanical durability can be established: garnet > quartz > epidote ≥ volcanic rock fragments ≥ feldspars > opaques ≥ pyroxene > amphibole > sedimentary/metasedimentary rock fragments. It is clear from multiple experiments, theoretical work and field observations from multiple localities that K-feldspar (as well as many other minerals) rounds quickly when subjected to eolian conditions. We argue, based on experimental work and field observations, that supposed ancient ergs should contain an abundance of well-rounded K-feldspar grains (along with other rounded to well-rounded minerals). In field outcrops, it is often easy to establish whether angular K-feldspar grains could have been supplied from nearby crystalline sources or from aqueous sources such as streams or beaches. In the absence of such data, the presence of angular K-feldspar in ancient sandstones should be a reliable indicator of 1) a first-order cycle of at least some of the sediment and 2) aqueous transport and depositional processes of the sandstone being considered. Angular K-feldspar argues strongly against an eolian origin for sandstones especially if it is found centrally located within these ancient sand bodies, 100’s of kilometers from potential sources that could supply angular grains. In the cases where we found angular K-feldspar in modern desert sand (Figs. 11-12), there was always a nearby source for the angular grains such as an igneous pluton, beach, or wadi. Often these sources were no more than a few kilometers distant. However, when considering whether angular K-feldspar in the Coconino (and its correlatives) were deposited by eolian processes or not, how could angular feldspars reach the center of that giant “erg” without becoming rounded? Angular K-feldspar was not only found along the edges of the Coconino sand body, but everywhere we sampled. Samples were collected from the entire exposed breadth and width of the Coconino. Modern observations have shown that angular K-feldspar does not have a reasonable way to be transported to the middle of an erg, except perhaps by fluvial transportation. Observations and experiments show that it is unlikely to be transported more than a few kilometers by known eolian processes without becoming quickly rounded by abrasion. There is no sedimentological evidence within the midst of the Coconino sand body that any of the deposits are beach, nearshore or fluvial in origin, which would be the most reasonable source for the angular K-feldspar. Many of the Coconino’s correlatives (Fig. 13), and units that Whitmore and Strom ◀ Angular K-feldspars in ancient sandstones ▶ 2018 ICC 641