Figure 5. Early in our study we obtained low-altitude, oblique aerial movie footage of this location we call “Nate’s Hill.” Landform aerial overflight video was edited and posted so we could invite specialists to give us their opinions (Loper, 2022b). We recognized a 25-square-kilometer area of interest (Figures 6 and 7). Figure 6 is the portion of the Anderson Canyon USGS 1:24,000 scale topographic map. Figure 7 is the published USGS Flagstaff 30’ x 60’ geological quadrangle map of Billingsley et al. (2013). We used the map and report of Billingsley et al. (2013) as our introductory framework for bedrock structure and stratigraphy. We greatly expanded our understanding of bedrock structure through field study at the landform tract. Next, we assembled satellite imagery from Google Earth to form a half-meter-resolution composite, vertical image collectively composed of about 100 million pixels. Upon the composite, highresolution image, we overlayed a two-meter contour interval map from the USGS digital elevation model (DEM). The 25-squarekilometer composite landform tract image with overlain contour lines is rendered in lower resolution in Figure 8. Our attention became focused on 13 “landform fields” within Figure 8. Those 13 “landform fields” are numbered in Figure 8, and we selected four fields for the most detailed study. Each of these four fields is depicted as an added figure. Figure 9 is field 2 which we call “Interstate Highway Arch.” Figure 10 is field 4 which we call “Chevron Hill.” Figure 11 is field 7 which we call “Nate’s Hill.” Figure 12 is field 8 which we call “Graben Hill.” Finally, and most important for methodological discussion, we studied the landforms in the field. We observed the stratigraphy of the outcropping Harrisburg Member at the top of the Kaibab Formation, and related the landforms to the faults and folds that form the bedrock ramp structure of the southern margin of the Colorado Plateau just north of the Mogollon Rim. OBSERVATIONS—STRUCTURE AND STRATIGRAPHY Figure 7 is the relevant portion of the geologic map of Billingsley et al. (2013) showing the 25-square-kilometer research area. It displays the limestone ramp of Kaibab Formation that descends from southwest to northeast, away from the Mogollon Rim and through the landform tract. The ramp dips northeastward with slope 0.01(rise over run 1:100) and primarily exposes the uppermost beds of the Harrisburg Member of the Kaibab Formation (light blue in Figure 7). Two secondary geologic structures occur on the ramp. The first is gentle, northeast-trending, plunging anticlines and synclines. The plunging anticline axis runs northward through “Interstate Highway Arch” (field 2). That feature has limestone strata dipping westward on the west side of the hill and eastward on the east side of the hill. The northern side of Wagon Box Draw is a consequence of a very gentle plunging syncline, and the limestone outcrop called “Nate’s Hill” (field 7). The north side of Wagon Box Draw at “Nate’s Hill” is the limestone northern limb (dip slope) of the gently plunging syncline. The slope of “Nate’s Hill” is 0.02 (rise over run 1:50) and is a two-component system (0.01 + 0.01 = 0.02) being composed of the ramp’s slope (0.01) added to the anticline’s slope (0.01). The second structure superimposed on the ramp is a suite of northwesttrending graben structures expressed at northwest-trending listric normal faults. Strata of Moenkopi Formation (green in Figure 7) and Quaternary-Pliocene gravels (yellow in Figure 7) are frequently depressed within these grabens. The stratigraphy within the primary ramp is best displayed in Figure 13 just 3.7 kilometers northeast of the landform research tract (just off the northeast corner of Figure 7). There deep erosion Figure 6. Portion of Anderson Canyon 1:24,000 USGS topographic map of the 25-square-kilometer Wagon Box Draw study area (large red square). The contour interval is 20 feet. Section boundaries (inset red grid) are onemile squares. Figure 7. Geologic map of the Wagon Box Draw study area (large red square is 5 kilometers on each side). Light blue is Kaibab Formation. Green is Moenkopi Formation. Repeating square grid pattern contains 1-mile-wide section boundaries. Geologic base map is after Billingsley et al., 2013. approaching 1860 meters. These landforms occur just south of Interstate Highway 40 at the Buffalo Range Road exit (Arizona I-40, exit 225) about 45 kilometers east of Flagstaff, Arizona. Figures 3 and 4 show the geographic context of what we call “Wagon Box Draw Landform Tract.” The area of interest is 18 kilometers westnorthwest of Meteor Crater, Arizona. In this region, most land is administrated by the Hopi, and the tract is used primarily as cattle rangeland. We discovered, upon viewing satellite imagery, a complex of terracelike landforms at 1740 meters (5,700 feet) elevation in the drainage called Wagon Box Draw, an example of which is shown in AUSTIN, HOLROYD, FOLKS, AND LOPER Shoreline Transgressive Terraces 2023 ICC 350
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