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

(Blakey and Knepp 1989, p. 336). Some authors also report that cross-bedding style, dip direction and grain size in the Toroweap is indistinguishable from the Coconino in the Oak Creek Canyon area, causing them to think part of the Toroweap is eolian (Rawson and Turner-Peterson 1980). Blakey (1990) names the upper part of the Coconino the “Cave Spring Member” and claims that it grades laterally into the Toroweap according to data from Rawson and Turner-Peterson (1980). The Coconino also grades into Toroweap at locations above the Coconino. In northern Arizona, Billingsley and Dyer (2003) report that the Coconino occurs as a thin and discontinuous cross-bedded unit incorporated within the base of the Toroweap. The Coconino probably correlates with the Scherrer Formation, which is a marine sandstone, in southeastern Arizona (Blakey 1990, p. 1216) and transitions eastwards into the Glorieta Sandstone of New Mexico which is also thought to be marine (Baars 1961, p. 199). Whitmore and Garner (2018, in these proceedings) provide some more of these details. Some of the Coconino’s correlatives are discussed in Appendix I, and the references there provide evidence for the marine origin of many of these units. Thus, we do not find it surprising that angular K-feldspar grains occur in the Coconino and its equivalents. It is believed that the source of the Coconino sand, based on analysis of zircons (Gehrels et al. 2011, p. 197), is from the mid- Proterozoic rocks of eastern North America, or possibly, but less likely, from the Ouachita orogen. These authors 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 NorthAmerica 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 angular K-feldspar and mica (Borsch et al. 2018), we feel that some type of aqueous transport was primary. Any eolian transport would have quickly rounded the K-feldspars and caused the micas to disappear. In light of the fact that angular K-feldspars are not expected in eolian sandstones, it is odd that we have these types of grains in so many supposedly eolian sandstones from all over the world, not just the Coconino. Either every one of these sandstones must have had a very nearby K-feldspar source during its deposition, or perhaps they are not eolian. We have not extensively sampled all of the formations in this paper (with the exception of the Coconino). But, with the Coconino in particular, there are no nearby beaches, K-feldspar bearing outcrops or known fluvial deposits within the formation. This might be more likely with some of the other formations mentioned in this report. Many of the same sandstones that have angular K-feldspars also contain angular grains of quartz, mica flakes (mostly muscovite) and are moderately to poorly sorted (Whitmore et al. 2014; Maithel et al. 2015). In other words, under the microscope these sandstones are not as texturally mature as they might appear to be at the outcrop or assumed to be from their purported eolian origin. As discussed earlier, many criteria for eolian sandstones have been suggested, but very few of the criteria are actually applied except for large scale cross-strata and “high” dip angles. FURTHER WORK We encourage further petrographic work on many of the sandstones that we have listed in Appendix I. In the past, detailed microscope work has often been ignored because it can be time consuming to collect, prepare and study the samples. However, this kind of work provides details that are often important for paleoenvironmental interpretations—perhaps even more important than outcrop observations. Several authors have suggested (Odom 1975; Odom et al. 1976) that K-feldspar is more abundant in sandstones with smaller grain sizes. Work is needed that compares the roundness of similar sized quartz and K-feldspar grains. Similar studies should also be done in modern eolian deposits. This work would be time consuming, but may show some interesting results. We suspect it will show that K-feldspar is often more rounded than similar-sized quartz grains. In ancient sandstones we think it will show that K-feldspar is only slightly more rounded than quartz if not equally rounded as quartz. This could probably be done more easily with modern dunes because those samples can be easily sieved to segregate grain sizes. The process is a bit more difficult with cemented sandstones, but some progress has been made by S. Maithel (2018 personal communication) by using a sonicator to disaggregate sand grains from the Coconino Sandstone as part of her PhD work. CONCLUSION K-feldspar sand is often second in abundance to quartz in many ancient cross-bedded sandstones that are often interpreted as partially or completely eolian in origin. On Mohs scale of hardness, K-feldspar has a hardness of 6.0, whereas quartz has a hardness of 7.0. K-feldspar cleaves relatively easily compared to the conchoidal fracture of quartz. Because of these differences, theoretical, experimental, and field observations (in a wide variety of settings) have shown that K-feldspar rounds much easier than quartz in eolian settings. Under aqueous conditions, it is now undisputed that even energetic aqueous conditions (such as longshore currents and daily tidal currents) are insufficient to round any minerals. It is believed that differences in rounding between eolian and aqueous environments are due to the ability of water to cushion impacts between grains; something that air is incapable of accomplishing in the eolian environment, thus causing rapid rounding. In settings where angular sand grains are present on a beach and they are picked up and transported to coastal dunes, rounding has been documented to happen very quickly and over short distances. In fact, many authors now believe that eolian activity is the only reasonable way to round resistant grains such as quartz (see Dott 2003). However, it should be noted that many quartz and K-feldspar grains do not become rounded in eolian settings if a source for angular grains is nearby. Thus, we argue that when angular K-feldspar sand grains are present in ancient cross-bedded sandstones, especially “blanket sandstones” (Baars 1961), it is a primary criterion that should be considered when determining the origin for a sandstone. We have documented that many supposed eolian sandstones contain angular K-feldspars suggesting that they had an aqueous origin. ACKNOWLEDGMENTS Most of the samples used in this work were collected as part of the FAST project to study the Coconino Sandstone during the years between 2007 and 2011 which was partially funded by ICR. Other parts of this project were funded by Calgary Rock and Materials Services Inc. and private sources. Cedarville University provided logistical support. The authors thank the many people who have provided help, support and funding over the years. Special thanks also go to Paul Garner who helped collect many of the studied samples and has been an integral part of the entire Coconino Sandstone project. We thank the suggestions of anonymous reviewers who helped improve this manuscript. Whitmore and Strom ◀ Angular K-feldspars in ancient sandstones ▶ 2018 ICC 643