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-10- <br /> <br />an abundance of sediments to the east and to the west. The present <br />topography had its origins during the Quaternary when uplift and heavy <br />erosion dissected through the sediments which had been accumulating <br />almost continuously since the Lower Cretaceous. Thus the more erodable <br />Mancos Shales produced the Axial Basin, while the more resistant sand- <br />stones of the Mesaverde were left as mountains surrounding the Basin. <br />Due to the geomorphology of the Craig area, the Williams Fork <br />Formation comprises the bulk of the surface rock. It is not surprising <br />then, that the majority of the fossils collected came from this deposit <br />with only a minor and insignificant amount of material collected from <br />the other formations. The major fossils and fossil localities are <br />plotted in Fig. 1, and are listed below: <br />A-1 Located in the northern part of the Colowyo Mine property, <br />this locality produced numerous angiosperm leaves in a <br />yellow, fine to medium grained sandstone. <br />A-2 Not far from A-1 an unidentified plant stem was collected <br />in a pinkish shale. <br />A-3 Angiosperm leaves were found in a reddish sandstone. <br />A-4 In the cliffs north of the Colowyo Mine office, at the mouth <br />of Streeter Canyon, is exposed beds of the cyclothem type. <br />The exposure shows a sequence of calcareous shales, carbona- <br />ceous shales, coal, shales or siltstone, often rich in fossil <br />plants, and fine to medium grained sandstones. This series <br />repeats several times in the cliff face. Most of the fossils <br />of this locality were collected in the lowermost shales and <br />• <br />