Depicting Grand Canyon's Rock Layers: 150 Years of Visualizing And
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Depicting Grand Canyon’s rock layers: 150 years of visualizing and interpreting geology Karl Karlstrom and Laurie Crossey, University of New Mexico These color and supplementary figures accompany the following reference: Karlstrom, K. E., and Crossey, L. J., 2020, Depicting Grand Canyon’s Rock Layers: 150 years of Visualizing and Interpreting Geology: in, Quartaroli, Richard, editor, Celebrating 100 Years of Grand Canyon National Park: A Gathering of Grand Canyon Historians: Ideas, Arguments, and First-Person Accounts, Symposium Proceedings of the Grand Canyon Historical Society, (Grand Canyon, Ariz.: Grand Canyon Conservancy, 2020, v. 5, chapter 31, pp. xx –xx. 1 Figure 31-1. John Strong Newberry’s (1856) rock column was developed from examination of strata in Diamond Creek and the Aubrey cliffs. As Edwin Mckee wrote: “their conclusions were remarkable considering the difficult conditions under which they worked and the state of general knowledge at the time.” Red boxes summarize early correlations made by Markou (1856) and Newberry (1861). Supplemenary Figure 31-1B. Friedrich W. Von Egloffstein’s engraving Black Canyon was made from a sketch of Lieut. Ives and is Plate V. of the Ives report. 2 Figure 31-2. John Wesley Powell Figure 31-3. The lower nonconformity recognized two major unconformities that drawn correctly (by the author’s UNM bound the three main sets of rock but the graduate student Micah Jessup) shows a strata above the lower unconformity were depositional (but now-tilted) contact depicted incorrectly. above the basement. Powell corrected this error (but not the drawing) in his next rock column in 1876. 3 Figure. 31-4. Block diagrams in Powell (1875) set a high standard for showing how rock strata influence landscapes. 4 Figure. 31-4. Block diagrams in Powell (1875) portrays the regional landscape in bird’s-eye view, and major faults in cross sectioal view. 5 Supplementary Figure 31-4B. The east side of Plate XXIX of Dutton (1882) showing labeled rock units (1-9). White boxes show rock names they assigned in their key (followed by new names labeled by KEK). B. Tower of Babel; C. Colorado River; l. Inner Gorge. 6 Figure 31-5. The iconic rock column depiction of Grand Canyon’s three sets of rocks as shown by Sharp (1940). Figure 31-6. The iconic rock column depiction of Grand Canyon’s three sets of rocks as shown by Maxon (1968). 7 Supplementary Figure 6. The iconic rock column depiction of Grand Canyon’s three sets of rocks and the canyon weathering profile was modified from 6A) Powell (1876; upper left) and 6B) Levi Noble (1914; lower left). It has been refined by many authors , for example 6C) Breed (1972; upper right), among others. 8 Supplementary Figure 31-6D. N.H. Dutton (1910; USGS Bulletin 435, p. 21) incorrectly showed the Unkar Group to be conformable with the Tonto Group. Supplementary Figure 31-6E. N.H. Dutton and others (1916; USGS Bulletin 613, p. 130) correctly showed the Unkar Group at an angle below the Tonto Group. This was part of a Guidebook of the Western United States, Part C. The Santa Fe Route, with a side trip to the Grand Canyon of the Colorado. 9 Figure 31-7. LaRue (1925) showed the Colorado River and Grand Canyon’s cross sectional profile drawn parallel to the river between Lees Ferry and Parker Arizona and how the rock layers rise from it. This is an excellent depiction of how Grand Canyon deepens abruptly below Lees Ferry and ends abruptly at Grand Wash cliffs. )U.S. Geological Survey, Water Supply Paper 556, Plate XV). The gray color for the proposed reservoirs was added by us. 10 Figure 31-8. The iconic rock column Figure 31-9. Rock column in the Yavapai depiction of Grand Canyon’s three sets of Geology Museum (1932 NPS photo of rocks was interpreted in the early 1930s in ranger Ralph Reburn and tourists). the Mary Colter fireplace at Bright Angel Annotations are added for clarity. Lodge 11 Figure 31-10. In the 1960s, Inner Canyon geology interpretation on Kaibab and Bright Angel Trails used a version of the Noble (1914) rock column and showed “This Exhibit” at every rock contact where hikers (like Karl as a youth) learned the layer names and some basic geology. 12 Supplementary Figure 11A. This classic cross section from McKee and Resser (1945) illustrates the concept of how beach sands migrated east across the Great Unconformity followed in a given location by offshore muds, then limestones, during Cambrian flooding of the continent. Supplementary Figure 11B. New dating adds the Sixtymile Formation and Frenchman Mountain Dolostone to the Cambrian Tonto Group (Karlstrom et al., 2018) as illustrated by a similar depiction. 13 Supplementary Figure 12A. Elston and McKee (1982) published an innovative rock column diagram that depicts the tilt of the Grand Canyon Supergroup layers, their scaled stratigraphic thickness (nearly 4 km!), and the importance of the Butte fault. Supplementary Figure 12B. Newer geochronology has led to revised nomenclature such that Nankoweap Formation is considered part of the Chuar Group and the Sixtymile Formation is part of the Cambrian Tonto Group. 14 Supplementary Figure 13A. Entry portals for the Trail of Time Exhibit used a veneer of the real rocks collected along the river to depict the three sets of rocks, two major unconformities, the canyon erosion profile, and the inner gorge. Supplementary Figure 13B. Grand Canyon’s rock column seems impressively complete, but the time column shows how much time is missing (in black). 15 Figure 14A. Evaluation of visitor understandings conducted during development of the Trail of Time exhibit confirmed that 3-D depictions were effective at connecting rock layers to landscapes. This block diagram appears on several signs on the Trail of Time exhibit. Figure 14B. A new rock column shows all Grand Canyon strata at scaled thickness, major unconformities, the importance of fault reactivation, and water pathways. This one was prepared By the authors in 2019 and drafted by Tom Patterson of Harpers Ferry office for the Grand Canyon National Park Entrance Station hand-out called the Unigrid. 16 Supplementary Figure 15. Stratigraphic column of rocks of the Grand Canyon region showing the three sets of rocks, correct stratigraphic thicknesses for all stratified rocks, numeric ages of units based on geochronology, major unconfromities (red) and time missing (not recorded) at each, faults, and water pathways; from Karlstrom and Crossey (2019). 17.