Figure 3. Eolian crossbeds in Chuska Sandstone (Narbona Pass Member) at ∼2950 m elevation near Roof Butte, northern Chuska Mountains. Hammer for scale at center of photograph.

Figure 9. Changes with publication time in inferred derivation of the Chuska Sandstone. The Deza Member (A–C in figure) is fluvial; the Narbona Pass Member (D) is eolian. Cather et al. (2003) proposed that streams flowing southwest from the San Juan Mountains produced a piedmont that extended

Figure 2. (A) Digital elevation model for the Chuska Mountains area. Flat top of the southern Chuska Mountains is defined by silica-cemented zones within the Chuska Sandstone that formed during early, phreatic diagenesis (see text). Note the eastern boundary structure of the Laramide Defiance

Figure 15. Late Eocene to Recent aggradation and exhumation history of the central and southern Colorado Plateau relative to present-day elevations, based on a conservative (minimum) estimate of elevation of Chuska erg surface. Note that the Chuska Sandstone and Bidahochi Formation outcrops

Figure 15. Late Eocene to Recent aggradation and exhumation history of the central and southern Colorado Plateau relative to present-day elevations, based on a conservative (minimum) estimate of elevation of Chuska erg surface. Note that the Chuska Sandstone and Bidahochi Formation outcrops

Figure 4. Thin section of eolian sandstone of Narbona Pass Member of the Chuska Sandstone showing isopachous rims of chalcedony cement, indicative of cementation in a phreatic environment. Width of field is 0.5 mm.

Figure 9. Topographic profile A–A′ (see Fig. 8 for location) of basal contacts of Miocene Bidahochi Formation and Eocene–Oligocene Chuska Sandstone from French Butte (on the southwest) along the alignment of ancestral Pueblo Colorado Wash ( Fig. 2 ) past Ganado ( Figs. 2 , 8 ) to the Sonsela

FIG. 1. —Index map of northeastern Arizona and adjacent parts of New Mexico, showing distribution of upper and lower members of Bidahochi formation and of Chuska sandstone. Distribution of volcanic member of Bidahochi formation is not shown.

the projection of the Crooked Ridge paleoriver. The approximate 35 Ma and 27 Ma sub–Chuska Sandstone and top–Chuska Sandstone surfaces are shown as orange dashed lines. The late Oligocene San Juan Mountains profile (gray) is depicted as originally grading to the top of the Chuska Sandstone ( Cather et al., 2008

on oagc 15, and text page 80. (2) Allen’s interpretation of Gregory, as inferred from Allen’s text and from personal corrcspondence. (3) Inferred from Silver’s text. (4) Acceptance of Allen’s interpretation, with new subdivision ot Chuska sandstone.

grains from individual samples; note significant number of ca. 2 Ma grains from four out of five White Mesa alluvium samples and the presence of ca. 9 Ma grains in all samples. (C,D) Summary of 20–40 Ma detrital sanidine grains. (C) Groupings as in A with addition of Chuska Sandstone (purple). All show

Figure 5. Chronostratigraphic correlation diagram for eolianites and associated rocks in the Chuska Mountains and the Mogollon-Datil volcanic field. (A) Chuska Mountains, showing members of Chuska Sandstone. (B) Western Mogollon-Datil field. (C) Northern Mogollon-Datil field. See text for sources

are in Kimbrough et al. (2015) ; Chuska Sandstone data are in Dickinson et al. (2014) . Explanation as in Figure 11 (4% of grains older than 2000 Ma omitted from plots). N—number of samples; n—total number of detrital zircon grains. Note the lack of 35–23 Ma grains from San Juan Mountains volcanic field in San