 In extent, the basin is approximately east-west, and north-south, in Huerfano and Las Animas Counties, Colorado, and Colfax County, New Mexico.The basin has long been a source of coal, and more recently of coalbed methane.It is known for its well-preserved exposures of the Cretaceous–Paleogene boundary (K–T boundary), which has been intensively studied for evidence of meteorite impact.