Pliocene and Pleistocene geologic and climatic evolution in the San Luis Valley of south-central Colorado - Rogers, K.L.; Larson, E.E.; Smith, G.; Katzman, D.; Smith, G.R.; Cerling, T.; Wang, Y.; Baker, R.; Lohmann, K.C.; Repenning, C.A.; Patterson, P.; Mackie, G. (Palaeogeography, Palaeoclimatology, Palaeoecology, 1992)