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

Whitmore, J.H., and R. Strom. 2018. The significance of angular K-feldspar grains in ancient sandstones. In Proceedings of the Eighth International Conference on Creationism , ed. J.H. Whitmore, pp. 628-651. Pittsburgh, Pennsylvania: Creation Science Fellowship. THE SIGNIFICANCE OFANGULAR K-FELDSPAR GRAINS IN ANCIENT SANDSTONES John H. Whitmore , Cedarville University, 251 N. Main St., Cedarville, OH USA 45314 johnwhitmore@cedarville.edu Raymond Strom , Calgary Rock and Materials Services Inc., #3, 3610-29th St. NE, Calgary, Alberta, Canada T1Y 5Z7 rocktell@telus.net ABSTRACT In our studies of ancient sandstones, many of which are purported in the conventional literature to be eolian deposits, we frequently encountered angular K-feldspar sand grains. In particular, we encountered them while studying the Coconino Sandstone of Arizona, but we have found them in many other ancient sandstones as well. To gain some insights on the petrology of ancient “eolian” sandstones, we studied the petrology of a number small ergs in the western United States, beach and dune sands along the California and Oregon and reviewed the literature on the petrology of modern eolian and subaqueous deposits. In our literature review and from our own observations along the California and Oregon coastlines, we found that fluvial and shoreline processes are not sufficient to cause rounding of sand grains of any type, even after energetic and prolonged longshore transport and frequent tidal activity. Conversely, when sand grains are picked up by eolian processes and transported to coastal dunes, all species of mineral grains are quickly rounded, even over short distances. K-feldspar is rounded faster than quartz probably because it is softer and cleaves easier. We frequently encountered rounded K-feldspar grains in the small ergs we examined despite many of them being close in proximity to sources of angular K-feldspar sand grains. In larger ergs, all types of sand grains become quickly rounded and angular grains only occur if there are local fluvial or coastal sources for them. The frequent occurrence of angular K-feldspar grains that we found in ancient cross-bedded sandstones, purported to be made by eolian processes, causes us to question whether these deposits were made by eolian activities or not. The presence of angular K-feldspar may be one petrographic criterion for identifying ancient fluvial and marine deposits. The goal of this paper is to document the ubiquitous occurrence of angular K-feldspar grains in many supposed ancient cross-bedded sandstones. Coupled with other criteria, angular K-feldspar sand grains are a crucial piece of data that might be used to argue that these ancient sandstones were formed by aqueous rather than eolian processes. KEY WORDS K-feldspar, abrasion experiments, rounding of K-feldspar, rounding of quartz, Aztec Sandstone, Bridgnorth Sandstone, Casper Sandstone, Cedar Mesa Sandstone, Coconino Sandstone, Corrie Sandstone, Hopeman Sandstone, Locharbriggs Sandstone, Lyons Sandstone, Navajo Sandstone, Penrith Sandstone, Schnebly Hill Formation, Tensleep Sandstone, Weber Sandstone, Yellow Sand Copyright 2018 Creation Science Fellowship, Inc., Pittsburgh, Pennsylvania, USA www.creationicc.org 628 INTRODUCTION In our studies of thin sections from the Coconino Sandstone, we encountered angular K-feldspar sand grains that were sometimes more angular than the similar-sized quartz grains that surrounded them (Whitmore et al., 2014). We found this to be unusual because K-feldspar has a hardness of 6.0 on Mohs scale of hardness, while quartz has a hardness of 7.0. To better understand our Coconino data, a series of modern sand samples were collected to investigate the rounding rates of sand. We chose to study the rounding of quartz and K-feldspar grains as they were transported by eolian processes from beach to dune environments along the Oregon and California coastlines. The results of those studies have been reported in several places (Whitmore and Strom 2017a, 2017b; McMaster et al. 2010; McKevitt 2012) with the most extensive report published late last year (Whitmore and Strom 2017c). In that paper, we also reported on samples that we collected and studied from a number of small ergs in the western United States. We noted rounded and well-rounded K-feldspar was prevalent in those eolian dunes. Those studies concluded that both K-feldspar and, to a lesser extent, quartz sand can be noticeably rounded by eolian transport even over short distances (less than 0.5 km) as angular sand grains are carried from the beach to nearby coastal dunes. The change in rounding was statistically significant. In our observations, sometimes angular K-feldspar grains can occasionally be found in ergs, but it is only common when beaches, rivers or a plutonic source of bedrock provides a nearby source for the angular sand. Under normal conditions, K-feldspar in particular, becomes noticeably rounded even after being transported over distances as small as 125 m. It becomes rounded to well-rounded as it gets transported further into the erg. We used standardized rounding definitions that were developed by Powers (1953) and slightly modified by Folk (1955) and are illustrated in Fig. 1. Similar observations and conclusions were reached by Garzanti et al. (2012, 2015). They studied sand that was carried 100’s of kilometers from the Orange Delta northward along the Namibian coast by longshore and tidal currents. During aqueous transport the sand, it remained angular and the composition fairly constant. It wasn’t until eolian transport ensued, that sand grains of all types, became quickly rounded as they were transported to the nearby coastal erg. The conclusion of our previous studies was that rounded