A thick sequence of late Upper Cretaceous and Tertiary sedimentary rocks is preserved in the Raton basin. These strata include the Pierre shale, Trinidad sandstone, and Vermejo formation of Late Cretaceous age; the Raton formation of Late Cretaceous and Paleocene age; the Poison Canyon formation of Paleocene age; the Cuchara and Huerfano formations of Eocene age; and two newly defined formations, one probably Oligocene and the other probably Miocene in age. These rocks record some of the stratigraphic and structural events of the Laramide revolution.
In the southern Rocky Mountain region the Laramide revolution began with epeirogenic movements west of the Raton basin in late Montana time. The epeirogenic movements were followed by at least seven orogenic episodes, as shown by angular unconformities and lithologic features of the sedimentary rocks. During the Eocene the sedimentary rocks of the basin were intruded by igneous magma to form sills, dikes, plugs, stocks, sole injections, and laccoliths.