Deposition of the Burro Canyon Formation was brought to a close by
another uplift of the Plateau, and of course the uplift was followed by
another period of erosion, which continued through the end of Early
Cretaceous time. As noted in the caption for figure 24, seemingly all
but 58 feet of the Burro Canyon was eroded away, but 120 feet remains
along East Creek, only about 12 miles to the southeast, which suggests
that the old erosion surface was a bit uneven. That this period of
erosion was of considerable duration is suggested by the abundance of
the white clay mineral, kaolinite, beneath and in the overlying white
basal conglomerate of the Dakota Sandstone. This type of clay commonly
results from prolonged weathering of many types of rocks and indicates
that the period of pre-Dakota erosion was of long duration.