Cretaceous and Paleocene rocks of the Raton Basin, New Mexico and Colorado--Stratigraphic-environmental framework
— Charles L. Pillmore and Romeo M. Flores

The Late Cretaceous in the Raton basin was a period of emergence of land and retreat of the Cretaceous epeiric sea. The coastline advanced eastward across New Mexico, as broad prograding deltaic and barrier coastal plains were formed seaward of aggrading fluvial systems. This report discusses the marine and marginal-marine formations and the rocks that were deposited by fluvial systems that drained the episodically emergent San Luis highland (Tweto, 1980) during the Late Cretaceous and Paleocene in the Raton basin. The uppermost Cretaceous and Paleocene rocks in the Raton basin are the marine Pierre Shale (Campanian to Maastrichtian), marginal-marine Trinidad Sandstone (Maastrichtian), nonmarine coal-bearing Vermejo Formation (Maastrichtian), nonmarine coal-bearing Raton Formation (Maastrichtian and Paleocene) and nonmarine non-coal-bearing Poison Canyon Formation (Maastrichtian and Paleocene).