Some have recognized that supposed eolian cross-bedded sandstones often lack angle of repose cross-bed inclinations (3334°) which are common in modern eolian environments. It has previously been reported that sandstones like the Coconino have average cross-bed inclinations of only 20° and lack angle of repose inclinations. Compaction of the dip angles or nonpreservation of upper, and steeper, inclinations is often cited to explain this anomaly. Some (incorrectly) claim that subaqueous cross-bed inclinations are less than eolian ones, arguing that relatively low cross-bed angles and averages, like those in the Coconino, demonstrate a subaqueous origin rather than an eolian one. This study examined and compared over 10,000 cross-bed dip measurements from ancient sandstones (many supposed to be eolian) and modern eolian dunes. Modern dunes do not have the upper part of the dunes eroded away, so it is possible to measure anywhere on the dune. Despite this, it was found that both groups had central tendencies near 20°. The difference in the data sets is best demonstrated by the standard deviations. The middle quartiles of sandstones occurred between 15-24° with a standard deviation of 5.7. The middle quartiles of modern dunes occurred between 9-27°, with a standard deviation of 10.1, nearly double that of ancient sandstones. In other words, modern dune inclinations had a much wider spread than ancient sandstones. Additionally, it was found that modern dunes often have inclination measurements of greater than 30°, which is uncommon in ancient sandstones. It was found that compaction is not a valid argument for lower-than-expected cross-bed angles, because modern dunes have an abundance of lower angles which are largely absent from the sandstone data sets. This study demonstrates that the spread of cross-bed dip inclinations in sandstones is the important criterion that distinguishes them from eolian deposits and suggests an alternative origin, not the averages of their dips. Additionally, it was found that some sets of sandstone cross-bed inclinations cannot be statistically distinguished from one another irrespective of presumed conventional depositional environment and cross-bed set thickness, specifically in the case of the Grand Canyon’s Coconino (eolian), Wescogame (fluvial), and Tapeats (shallow marine) Sandstones. ABSTRACT I. INTRODUCTION AND BACKGROUND The author has been working on the Coconino Sandstone (Permian, Arizona, USA) for about twenty-five years concluding that the sandstone formed in a subaqueous setting instead of the conventionally accepted desert dune environment (Whitmore and Garner 2018 and citations therein). This conclusion was based on textural, mineralogical, sedimentological, and facies relationship arguments. Maithel (2019) and Maithel et al. (2021) showed that the Coconino does not have the expected eolian-type sedimentology, as is often claimed (Middleton et al. 2003). During our work, we reported that average cross-bed dips in the Coconino were approximately 20° (Emery et al. 2011; Whitmore 2021a, 2021b; Whitmore and Garner 2018), consistent with what others have found in the Coconino for many decades (Maithel 2019; Reiche 1938). This paper is a formal presentation of the work presented in abstract form by Whitmore (2021a, b). Most geologists realize this average measurement (20°) is far less than the angle of repose for desert dunes, which is about 33-34°. The Coconino often lacks cross-bed dips in the thirties, leading to the erroneous conclusion by some that this conclusively demonstrates a subaqueous origin (Thomas 2021; Thomas and Clarey 2021). Many are unaware that the angle of repose is about the same in air as it is underwater (Allen 1970; Carrigy 1970; Hunter 1985), making steep angles underwater possible. On the other hand, some have erroneously claimed, without consultation of published literature, proper measurements, or data of their own, that the Coconino and other supposed eolian sandstones indeed have relatively steep crossbed dips near the angle of repose (Hill et al. 2016; Young and Stearley 2008; Strahler 1999). Inconsistently, some authors also want to claim that the cross-beds in “eolian” sandstones like the Coconino and Navajo are “steep” –at the angle of repose yet claiming at the same time the reason authors like myself have not encountered them is that the steeper tops of the eolian dunes have not been preserved (Collins John H. Whitmore, Cedarville University, School of Science and Mathematics, 251 N. Main St., Cedarville, Ohio 45314. johnwhitmore@cedarville.edu. © Cedarville University International Conference on Creationism. The views expressed in this publication are those of the author(s) and do not necessarily represent those of Cedarville University. 9th 2023 Whitmore, J.H. 2023. Can sandstone cross-bed dip inclinations determine depositional environment? In J.H. Whitmore (editor), Proceedings of the Ninth International Conference on Creationism, pp. 588-610. Cedarville, Ohio: Cedarville University International Conference on Creationism. CAN SANDSTONE CROSS-BED DIP INCLINATIONS DETERMINE DEPOSITIONAL ENVIRONMENT? KEYWORDS cross-bed dips, cross-bed inclinations, Coconino Sandstone, Tapeats Sandstone, Navajo Sandstone, eolian cross-beds, angle of repose, cross-bed statistics
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