Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2004

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Claim CC365.1:

Source:

Response:

1. Eolian (wind-blown) and subaqueous dunes have superficial similarities, but they differ in particulars. There is a great deal of diverse evidence that the Coconino Sandstone originated as eolian desert dunes. As McKee (1979, 204) stated:

   The basis for considering the Coconino Sandstone to be of eolian origin involves numerous criteria, some of which are distinctive of an eolian environment and others merely compatible with but not diagnostic of it. No single type of evidence seems entirely conclusive, but, together, the various features present very strong evidence. The principal criteria of dune deposition are as follows:
   
   

   1. The extent and homogeneity of the sand body.
      
      
   2. The tabular-planar and wedge-planar type and large scale of cross-stratification. The common high-angle deposits are interpreted as slipfaces on the lee sides of dunes, and the relatively rare low-angle cross-strata that dip toward the opposite quadrant apparently represent deposits of windward slopes.
      
      
   3. Slump marks of several varieties preserved on the steeply dipping surfaces of lee-side deposits. These are distinctive of dry sand avalanching.
      
      
   4. Ripple marks which are common on surfaces of high-angle crossbedding suggest eolian deposition both by their high indexes (above 15) and by their orientation with axes parallel to dip slope.
      
      
   5. The local preservation of a distinctive type of rain pit. Such pits illustrate the cohesion of sand grains with added moisture and a reorientation of the crater axes with respect to bedding slopes.
      
      
   6. Successions of miniature rises or steps ascending dip slopes of crossbeds.
      
      
   7. The preservation in fine sand of reptile footprints and probable millipede trails with sharp definition and clear impression.
      
      
   8. The consistent orientation of reptilian tracks up (not down) the steep foreset slopes.

   Since McKee published, additional types of terrestrial trace fossils, paleosols, and other distinctive eolian sedimentary structures have been recognized in Coconino and related eolian strata.
   
   If a person looks carefully at modern dunes -- for example, the Great Sand Dunes, White Sands, and Nebraska Sand Hills -- he or she will find an abundance of climbing translatent beds, with coarsening-up laminae and rare foreset laminae that form only by the migration and accretion of low-amplitude wind ripples in eolian environments. Such beds form only in terrestrial eolian environments and are completely absent from marine or lacustrine environments because the wind ripples that create them simply do not form under water and underwater analogues of these sedimentary. The fact that wind ripple and the distinctive bedding and laminations occur throughout the Coconino Sandstone and other similar strata -- for example, the Navajo and Entrada -- clearly refutes the marine hypothesis for their origin.
   
   
2. Sand waves deposited in water possess very low angle cross-beds, rarely steeper than 10 degrees. Cross-bedding in eolian dunes occurs at various angles. The general range in slope of the cross-beds is from 11 to 34 degrees. The average appears to be close to 25-28 degrees. The average slope of cross-bedding does not have to be equal to 30 to 34 degrees, which is the maximum slope of dry sand, to be from a sand dune. The maximum slope of cross-bedding within the Coconino Sandstone does get as steep as 30 to 34 degrees (McKee 1979; Reineck and Singh 1980). The 30-34 degree slope is produced from sand avalanching down the lee slip face of the dune. The beds and laminae produced by wind ripple migration can form cross-bedding and lamination that has slopes up to 20 degrees within a sand dune. Given that this cross-bedding is present everywhere in the Coconino Sandstone, it greatly decreases the average slope of the cross-bedding within the Coconino Sandstone. In addition, grain-fall processes produce low, inclined lamination and beds with slopes that average between 20 to 30 degrees and range from 0 to 40 degrees. The presence of grain-fall bedding and lamination within the Coconino, not only refutes the hypotheses concerning the underwater or marine origin of the Coconino Sandstone but also again greatly decreases the average slope of the cross-bedding found in the Coconino Sandstone. Thus, it is completely reasonable that the average slope of the cross-bedding in the Coconino Sandstone is less than the average slope of dry sand -- that is 30 to 34 degrees -- because the cascading of sand down the lee side of the sand dune is not the only process producing cross-beds and laminations in dune sands (Hunter 1977).

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