Abstract: "The Precambrian rocks of Colorado consist of a metaphoric complex more than 1,700 million years in age, three groups of igneous rocks about 1,700, 1,400, and 1,000 million years in age, here designated informal age groups, and two areally restricted units of sedimentary rocks, one between 1,400 and 1,700 million years in age and one between 950 and 1,400 million years. A systematic nomenclature for many of the rocks does not exist, but the present state of knowledge will permit establishment of a comprehensive nomenclature. Numerous formal names that have been applied to elements of the Precambrian assemblage are appraised and classified in a table, and eight names are abandoned."

A report about the lithologic units within a red-bed sequence that help to interpret the history and structure of the Woody Creek quadrangle, west-central Colorado.

A report about mapping in the northern and central parts of the Piceance Creek basin of northwestern Colorado where several relatively thin dominantly marlstone units tongue northward into the Eocene Uinta Formation.

A report about the Coughs Creek Tongue which is a sequence of light-gray marlstone, locally containing beds of sandstone and siltstone, in the upper part of the Green River Formation.

A report about the geology, composition, and stratigraphic nomenclature of the thirtynine mile volcanic field in central Colorado.

The following report presents a regional study of the extent, thickness, lithology, stratigraphic relations, age, depositional environment, and tectonic history of thick sulfate deposits and associated salts of sodium and potassium.