Circular 100 — The Tierra Amarilla Coal Field, Rio Arriba County, New Mexico

By Edwin R. Landis and Carle H. Dane, 1969, 14 pages.

The Tierra Amarilla coal field comprises a small block of coal-bearing rocks of the Mesaverde Group that lies on the east flank of the Chama basin about 12 miles east of the nearest outcrops of the Mesaverde on the northeast flank of the San Juan Basin. At the west end of the field, as many as nine coal beds are present but most are very thin and all are lenticular. The coal beds near the base of the coal-bearing sequence are thicker and more persistent and are locally as much as 49 inches thick. The coal, of subbituminous A rank, has been mined for local domestic use at several places in the western part of the field. A progressive east-ward change in lithology reduces the amount of carbona-ceous and clayey material in the Mesaverde to a very small amount and greatly increases the amount of sandstone in the unit. The Mesaverde also seems to thin to the east and northeast— the seaward direction at the time of deposition of the Upper Cretaceous rocks of the area.