Cross-bed Dips and Azimuths from Sandstones in the Western United States

In a paper that was published last year (Whitmore 2019), it was found that cross-bed dips of late Paleozoic sandstones of the western United States had consistent southerly cross-bed dips. Many of these sandstones (like the Casper, Coconino, DeChelly, Esplanade, Lyons, Tensleep, Weber and White Rim) are conventionally considered to be eolian (wind-blown) deposits–‒the dunes of which typically have foreset dips at or near the angle of repose (low thirties). However, it was found that average cross-bed dips of these sandstones are typically in the low twenties. Compaction cannot account for the low dips as thin sections show no signs of severe compaction, like significantly reduced porosity. It was concluded that low cross-bed dips were only one of many pieces of data that indicated these sandstones were water-deposited and not wind-blown. This project extends the previous work. We are compiling a data set of cross-bedded sandstones from the literature and from field work that includes formation name, age, location (latitude/longitude), number of measurements, strike, azimuth, dip angle and cross-bed set thickness. Data are placed into a spreadsheet so they can be evaluated mathematically with Excel and Oriana (a circular statistics package). The data from the western United States were plotted on a map for this symposium. It was found that the pattern of cross-bed dips in the low twenties is a consistent pattern for many of these sandstones, even for thick cross-bed sets of supposed eolian sandstones, like the Navajo Sandstone of Utah. This is somewhat of a surprise because most of these sandstones are often described as having “steep” cross-bed sets, meaning that it is supposed they were deposited near the angle of repose. The implications are significant, because they are consistent with the hypothesis that all these sandstones were deposited by Noah’s Flood and not by desert dune processes. Reference Whitmore, J.H. 2019. Lithostratigraphic Correlation of the Coconino Sandstone and a Global Survey of Permian “Eolian” Sandstones: Implications for Flood Geology. Answers Research Journal 12:275-328