Type of Submission
Poster
Keywords
cross-bed dip angles, Edwin D. McKee, Tapeats Sandstone, Manakacha Formation, Wescogame Formation, Pakoon Limestone, Esplanade Sandstone, Coconino Sandstone, Grand Canyon
Proposal
Edwin D. McKee (1906-1984) is widely recognized as the Grand Canyon’s most distinguished geologist. His monographs on the Canyon’s formations range from the Coconino Sandstone early in his career (1934) to the Supai Group late in his career (1982). Within his publications, extensive cross-bed dip data can be found for the Tapeats, Manakacha, Wescogame, Pakoon, and Esplanade units. McKee never published any of his own data on cross-bed dips of the Coconino (despite writing the seminal work on the topic), but he claimed in a 1979 publication that its dips mostly fell within the 25-30° range.
The purpose of this study is to statistically examine data published by McKee and Reiche to see if there is any difference in cross-bed dip angles between supposed subaqueous and eolian formations of the Grand Canyon area. McKee (1979) argued that “steep” cross-bed dips within the Coconino were one of the primary things that indicated it was an eolian sandstone. Many authors have argued that supposed eolian cross-beds are steeper than subaqueous ones. This project aims to test the validity of that claim.
Cross-bed dip data was gathered from papers by McKee and Reiche and then statistically analyzed with Excel and Grapher. Calculating ANOVA with Excel showed that the cross-bed dip angle populations of the Tapeats, Wescogame, and Coconino could not be distinguished from one another. Notched box and whisker plots drawn with Grapher visually confirmed these results. This is a significant and unexpected result because the three formations supposedly represent very different depositional environments within a conventional model: the Tapeats, a high-energy nearshore marine environment, the Wescogame, a high-energy fluvial environment, and the Coconino, eolian dunes deposited by wind. McKee’s claim that most dips of the Coconino fall within the 25-30° range are not supported by the data. Similar cross-bed dip populations between these three formations, all having median dips of about 20°, is further evidence that the Coconino was not deposited by eolian processes. Work is ongoing to compare these results with the dips of other cross-bedded formations and the cross-bed dips of modern eolian dunes.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Is There a Difference Between Supposed Eolian and Subaqueous Cross-bed Dips?
Edwin D. McKee (1906-1984) is widely recognized as the Grand Canyon’s most distinguished geologist. His monographs on the Canyon’s formations range from the Coconino Sandstone early in his career (1934) to the Supai Group late in his career (1982). Within his publications, extensive cross-bed dip data can be found for the Tapeats, Manakacha, Wescogame, Pakoon, and Esplanade units. McKee never published any of his own data on cross-bed dips of the Coconino (despite writing the seminal work on the topic), but he claimed in a 1979 publication that its dips mostly fell within the 25-30° range.
The purpose of this study is to statistically examine data published by McKee and Reiche to see if there is any difference in cross-bed dip angles between supposed subaqueous and eolian formations of the Grand Canyon area. McKee (1979) argued that “steep” cross-bed dips within the Coconino were one of the primary things that indicated it was an eolian sandstone. Many authors have argued that supposed eolian cross-beds are steeper than subaqueous ones. This project aims to test the validity of that claim.
Cross-bed dip data was gathered from papers by McKee and Reiche and then statistically analyzed with Excel and Grapher. Calculating ANOVA with Excel showed that the cross-bed dip angle populations of the Tapeats, Wescogame, and Coconino could not be distinguished from one another. Notched box and whisker plots drawn with Grapher visually confirmed these results. This is a significant and unexpected result because the three formations supposedly represent very different depositional environments within a conventional model: the Tapeats, a high-energy nearshore marine environment, the Wescogame, a high-energy fluvial environment, and the Coconino, eolian dunes deposited by wind. McKee’s claim that most dips of the Coconino fall within the 25-30° range are not supported by the data. Similar cross-bed dip populations between these three formations, all having median dips of about 20°, is further evidence that the Coconino was not deposited by eolian processes. Work is ongoing to compare these results with the dips of other cross-bedded formations and the cross-bed dips of modern eolian dunes.
