Second-day road log, from Gallup to Fort Wingate, Sixmile Canyon, Ciniza, Red Rock Park, Church Rock, White Mesa, Thoreau and Grants
— Spencer G. Lucas, Andrew B. Heckert, William R. Berglof, Barry S. Kues, Larry S. Crumpler, Jayne C. Aubele, Virginia T. McLemore, Donald E. Owen, and Steven C. Semken

The second day road log focuses on a detailed examination of the Triassic-Jurassic section of sedimentary rocks exposed on the northern flank (dipslope) of the Zuni Mountains. This is a classic section, first described in detail by Clarence Dutton in 1885. Though long studied, many aspects of these rocks remain controversial, and we explore some of these controversies.

Stop 1 dives right into debate about the base of the Chinle Group near Fort Wingate. Here, rocks of the Chinle Zuni Mountains Formation (“mottled strata”) are a paleoweathering profile riddled with large, vertical, tubular structures that have been variously identified as lungfish or crayfish burrows or as rhizoliths. We let you resolve this one.

Stop 2, a few miles to the east, in Sixmile Canyon, examines an unusual feature first described by Clay T. Smith—a paleokarst developed on top of the Permian San Andres Formation and filled with Triassic Moenkopi Formation debris. This lesson in “paleogeomorphology” is followed by Stop 3, farther down Sixmile Canyon, in extensive exposures of the lower part of the Chinle Group. Topics of discussion include Chinle sedimentation, basinwide unconformities and paleontology.

Stop 4 moves us up section into the Jurassic rocks at Red Rock Park. Here, we discuss controversies regarding regional stratigraphy and sedimentation of the Wingate, Entrada, Todilto, Summerville and Bluff formations. Stop 5, a few miles north, at White Mesa, exposes the top of the Jurassic section and the base of the Cretaceous Dakota Sandstone, which here is a spectacular, incised-valley fill.

The trip then continues east to Grants, with Stop 6 north of Thoreau at a quarry developed in limestone of the Jurassic Todilto Formation. Here, we discuss Jurassic sedimentation and industrial mineral production. The day ends at Grants.