Second-day road log: From Cortez to Mesa Verde National Park, Mancos and Durango
— Spencer G. Lucas, Orin J. Anderson, R. Mark Leckie, Robyn Wright-Dunbar, and Steven C. Semken

The route for Day 2 follows U.S. Highway 160 eastward from Cortez through Upper Cretaceous rocks. Beginning near the top of the Dakota Formation we climb into the Mancos Shale, which reaches a maximum thickness of 2300 ft locally, and ultimately reach the overlying Point Lookout Sandstone, a littoral and shoreface sandstone associated with a major regression during Santonian time. Subdivisions of the Mancos Shale, which are based mainly on the open-marine facies recognized east of here in eastern Colorado, will be examined as we enter the northern end of Mesa Verde National Park. A subsequent stop farther into the Park offers excellent views of the Mancos Valley and of the internal architecture of the Point Lookout Sandstone. As we journey eastward the very significant lateral changes in the Point Lookout-both in thickness and bedform-will be discussed in terms of depositional environments and position in the facies tract.

In Durango, at Horse Gulch, unusual sedimentary fractures in the Point Lookout Sandstone are well displayed as is the transition into the overlying, nonmarine coal-bearing section. On the north side of Durango we are treated to an excellent view of much of the Jurassic and Triassic section at Junction Creek. In descending order, the Jurassic section consists of the Morrison Formation, Junction Creek Sandstone (the lithostratigraphic equivalent and a synonym of Bluff Sandstone), a Summerville equivalent that includes a bed that has been called Bilk Creek Sandstone to the north near Ouray, the Pony Express Limestone (Todilto Formation), and the Entrada Sandstone. The underlying Upper Triassic rocks are assigned to the Chinle Group (local name- Dolores Formation) and consist of the Rock Point and Petrified Forest Formations and the Moss Back Formation at the base.

The base of the Morrison Formation here is very similar to that seen the previous day at Recapture Creek. The crossbedded sandstones of the Salt Wash Member rest unconformably on a thin, fine-grained red-bed sequence that in tum overlies the Junction Creek(= Bluff). The trip ends at our overnight accommodations in the Tamarron Lodge north of Durango.