  This narrative history of geologic and biologic events in the Great Plains had its origin in a study intended to identify potential National Natural Landmarks in the Great Plains, commissioned by the National Park Service. William A. Cobban, G. Edward Lewis, and Reuben J. Ross of the U. S. Geological Survey were collaborators in that study, and some of their contributions to the history of life on the Great Plains have been incorporated into this narrative, which was undertaken at the urging of Wallace R. Hansen. The photographic illustrations, other than those obtained from the film library of the U. S. Geological Survey, were provided by the interest and effort of my friends and colleagues of the Geological Survey—including C. R. Dunrud, V. L. Freeman, C. D. Miller, R. D. Miller, F. W. Osterwald, R. L. Parker, W. H. Raymond, III, Kenneth Shaver, and R. B. Taylor—and by Eugene Shearer, Intrasearch, Inc., Denver, Colo. Without their help this publication would not have been possible. |
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