Depositional environments and trace fossils of the Trinidad Sandstone, southern Raton Basin, New Mexico
— Charles L. Pillmore and J. O. Maberry

The Upper Cretaceous Trinidad Sandstone (Hills, 1899), the most widely exposed formation in the Raton Basin, records the final regression of the epeiric Western Interior Cretaceous seaway from northern New Mexico and southern Colorado. The shift from marine to continental conditions is reflected in the sequence of lithofacies and trace fossils in the Trinidad Sandstone. The Trinidad, which underlies Cretaceous and Tertiary coal-bearing rocks (Fig. 1), is a target in the search for oil, gas and the ground water that is vital to further coal development in the area.