From abstract: The Monument Valley-Navajo Mountain region is part of the Colorado Plateau and includes about 1,100 square miles in San Juan County, southeastern Utah, lying between the San Juan and Colorado Rivers on the north and the Utah-Arizona State line on the south. Included in the region are Navajo Mountain, the Rainbow Natural Bridge, and a part of the picturesque Monument Valley.

From introduction: The geologic record of the Tertiary period in the Green River Basin of southwestern Wyoming consists, in a broad way, of two quite different parts. The history of the first part, lasting through the Eocene epoch and perhaps on into the early Oligocene, was recorded in a thick series of sedimentary rocks of fluviatile and lacustrine origin. The history of the second part was recorded chiefly by successive stages of stream planation and stream trenching, but also in part by fluviatile sedimentation and, in certain localities, by glacial deposits. The first part of the record is virtually continuous, though its interpretation is by no means simple and obvious. The second part of the record is distinctly fragmentary, and the evidence the fragments provide is difficult to evaluate and to integrate.