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

angular K-feldspars in many ancient sandstones (Figs. 3-10) and rounded K-feldspars in modern eolian deposits (Figs. 11-12). Some angular grains were found in modern ergs, but only if the erg was near a source for the angular grains like a stream bed, beach or crystalline bedrock. Our results show examples of angular K-feldspar sand grains in many different sandstones from the western United States and Great Britain. The photographic plates are grouped by similar location or formation. Generally, the more photos we have of a particular sandstone, the more samples we collected from that particular unit. In these photos, blue is epoxy (or the empty space between grains), white is quartz or chert, red is calcite and yellow is K-feldspar. We found angular K-feldspars in virtually every sandstone that we examined . In the Coconino, this included all around the margins of the formation (top, bottom, edges) and in the middle of the sandstone. DISCUSSION In the sandstones that we studied, all have been reported to either be completely or partially deposited by eolian processes by many different authors (see Appendix I). Criteria cited for the eolian origin of many of these sandstones often include (see McKee and Bigarella 1979; Hunter 1977, 1981): 1) large scale cross-strata, 2) high dip angles near the angle of repose, 3) wind ripple marks that are perpendicular to the strike of the foreset beds, 4) slump marks and features, 5) contorted beds, 6) well-sorted sand, 7) fine to medium sized sand grains, 8) predominantly quartz in composition that are usually rounded to some degree, 9) pitted (frosted) sand grains, 10) animal tracks and trails, 11) interdune deposits, 12) non- marine fossil floras and faunas, 13) abrupt boundaries (meaning the sand deposits sharply interfinger with rather than grade into adjacent facies), 14) raindrop imprints, 15) lack of silt and clay in the deposit, 16) various types of characteristic laminae and strata including planebed laminae, rippleform laminae, ripple-foreset cross-laminae, climbing translatent strata, grainfall laminae, and sandflow cross-strata and 17) fine scale stratification associated with dune depositional processes. Often, many authors have not closely examined a sandstone in great detail before they arrive at a conclusion of an eolian origin. There are many examples where only large and steep cross-beds, sorting, rounding and frosting are the only criteria cited. This is especially true in the literature that has criticized creationists for thinking that the Coconino is a subaqueous deposit; albeit these authors are largely not specialists in eolian research (see for example, Hill et al. 2016; Strahler 1999; Weber 1980; Young and Stearley 2008). However, even specialists in eolian research have on occasion used sparingly few criteria in reaching an eolian conclusion for some sandstones (see McKee and Bigarella 1979). It turns out that many of the things that are often cited as “true” for a sandstone are not so after a more detailed examination. We found this to be the case in both the Coconino and Hopeman Sandstones when we examined the most often cited things such as cross-bed dips, sorting, angularity and frosting (Whitmore et al. 2014; Maithel et al. 2015). It is important to recognize that not all eolian sand grains become well-rounded and there are examples of desert dune sands that have angular grains within them (Pye and Tsoar 2009, p. 82-86). In particular, larger grains tend to get more well-rounded than smaller grains (Khalaf and Gharib 1985) and softer grains more rounded than harder ones (Pye and Tsoar 2009, p. 84). We found angular K-feldspar grains in our survey of small ergs in the western United States (Fig. 11-12). However, local sources for the angular grains could readily be identified from nearby (10’s of kilometers) wadis or igneous rock outcrops. In his study of sand grains in the Simpson Desert, Folk (1978) found that there was little appreciable rounding difference in the reg of the desert floor (originating from local streams) compared to the longitudinal dunes. Both quartz (predominant) and K-feldspar were angular to subangular. He attributed this to a short distance of grain transport to accomplish observable abrasion (p. 615, 621) and nearby fluvial origin of the sand (p. 616). It has been well-known for some time that aqueous transport does not appreciably round quartz or K-feldspar sand grains (Kuenen 1960; Russell and Taylor 1937; Twenhofel 1945). These views were confirmed by a noteworthy study of Garzanti et al. (2012; 2015), who investigated sand from the Orange River and Orange River Delta that empties into the Atlantic Ocean in southwestern Africa. Sand from these locations is carried northward along the African coast by continuous longshore currents and tidal activity, some of it for over 1400 km. After this great distance of transport and mechanical activity, all of the sand is still angular . The angular beach sand is then blown inland by southwesterly winds where it is deposited in the dunes of the Namibian Erg. They found that aqueous transport of beach sand, along the entire transport distance, fails to become appreciably rounded compared to the original river and delta sands. It is not until the wind picks up the sand and blows it into the erg does any appreciable rounding take place. Thus, in this study, rounding appears to happen only by eolian transport and not by any other mechanisms. Despite these studies, some have suggested K-feldspar can be successfully abraded in aqueous environments. Odom (1975) and Odom et al. (1976) studied a variety of quartz arenites. They observed that K-feldspar content increases with decreasing grain size. In many sandstones with mean grain sizes greater than about 0.177 mm (2.5 ϕ), K-feldspar is often less than 10% of the rock volume (which defines a quartz arenite). With grain sizes less than about 0.125 mm (3.0 ϕ), K-feldspar is often more abundant (10-25%), a rock which is called a feldspathic arenite. The authors suggest that this trend occurs because K-feldspar is abraded more easily in aqueous high energy environments (forming the larger- grained quartz arenites) and conserved in lower energy aqueous environments (forming the smaller-grained feldspathic arenites). There have been several explanations for how sand grains, especially more resistant quartz grains, become rounded (Chandler 1988; Dott 2003; Goudie and Watson 1981): 1) abrasion of sand grains by wind, 2) selective transport of better-rounded grains (to the dune) with the more angular ones being left behind in aqueous environments, 3) recycling of older deposits containing rounded grains and 4) intense chemical activity causing sharp corners of grains to be removed. Chemical activity can make a sandstone appear more “mature” by removing or altering more soluble grains such as feldspars; leaving quartz behind, especially in wet tropical environments. McBride (1985) referred to these as “diagenetic quartz arenites.” Of the four suggested mechanisms (above) for how sand grains become rounded, the current consensus appears to be only eolian transport, especially for the more mechanically and chemically resistant quartz grains (Chandler 1988). In environments like the hyper-arid Namib desert, eolian transport appears to be the only explanation because the major source of the sand grains is from Whitmore and Strom ◀ Angular K-feldspars in ancient sandstones ▶ 2018 ICC 630