ABSTRACT This field trip focuses on accessible and inclusive design in field-based teaching and learning through a broad investigation of the geology of Arizona, followed by more detailed exercises that focus on the Upper Triassic stratigraphic sequences in Petrified Forest National Park (PEFO). The first day of the field trip will traverse the three physiographic provinces of Arizona, from fault-bounded, basement-cored uplifts and valleys of the Basin and Range in the greater Phoenix area, through the Transition Zone to the Mogollon Rim, and ending in Upper Triassic sedimentary rocks of the Colorado Plateau at Holbrook. The second day of the field trip will encompass more detailed, collaborative exercises in PEFO that utilize the expertise of both student and faculty participants in mixed-ability groups. The main priority of this accessible field experience is the development of an inclusive community of learning driven by paired student-faculty interactions, facilitated as needed by technology integration to mitigate barriers and foster engagement, communication, and collaboration across a spectrum of ability and content knowledge. Please note that the collection of archaeological artifacts, fossils, rocks, or other natural history objects without an active research and collection permit is illegal at Petrified Forest National Park. Please refrain from collecting samples or specimens of any kind from anywhere in the park.

The source of volcanic material in the Upper Triassic Chinle Formation on the Colorado Plateau has long been speculated upon, largely owing to the absence of similar-age volcanic or plutonic material cropping out closer than several hundred kilometers distant. These strata, however, together with Upper Triassic formations within El Antimonio and Barranca Group sedimentary rocks in northern Sonora, Mexico, yield important clues about the inception of Cordilleran magmatism in Triassic time. Volcanic clasts in the Sonsela Member of the Chinle Formation range in age from ca. 235 to ca. 218 Ma. Geochemistry of the volcanic clasts documents a hydrothermally altered source region for these clasts. Detrital zircons in the Sonsela Member sandstone are of similar age to the clasts, as are detrital zircons from the El Antimonio and Barranca Groups in Sonora. Most noteworthy about the Colorado Plateau Triassic zircons, however, are their Th/U ratios, which range from ~1 to 3.5 in both clast and detrital zircons. Thorium/uranium ratios in the Sonoran zircons, in contrast, range from ~0.4 to ~1. These data, together with rare-earth-element geochemistry of the zircons, shed light on likely provenance. Geochemical comparisons support correlation of clasts in the Sonsela Member with Triassic plutons in the Mojave Desert in California that are of the same age. Zircons from these Triassic plutons have relatively low Th/U ratios, which correspond well with values from El Antimonio and Barranca Group sedimentary rocks, and support derivation of the strata, at least in part, from northern sources. The Sonsela Member zircons, in contrast, match Th/U values obtained from Proterozoic through Miocene volcanic, volcaniclastic, and plutonic rocks in the eastern and central Mojave Desert. Similarly, rare-earth-element compositions of zircons from Jurassic ignimbrites in the Mojave Desert, though overlapping those of zircons from Mojave Desert plutons, also closely resemble those from Sonsela Member zircons. We use these data to speculate that erosion of Triassic volcanic fields in the central to eastern Mojave Desert shed detritus that became incorporated into the Chinle Formation on the Colorado Plateau.