Professional papers. 690. Stratigraphy and origin of Chinle Formation and related Upper Triassic strata in Colorado Plateau Region [with list of references cited]; by J. H. Stewart, F. G. Poole, and R. F. Wilson, with section on Sedimentary petrology, by R. A. Cadigan, and section on Congolomerate studies, by William Thordarson, H. F. Albee, and J. H. Stewart.