Colorado National Monument, Colorado. South portal of the tunnel through Wingate Sandstone on the west side of No Thoroughfare Canyon above the east entrance.
Summary
Colorado National Monument, Colorado. South portal of the tunnel through Wingate Sandstone on the west side of No Thoroughfare Canyon above the east entrance. Figure 56, U.S. Geological Survey Bulletin 1508.
Summary
Colorado National Monument, Colorado. South portal of the tunnel through Wingate Sandstone on the west side of No Thoroughfare Canyon above the east entrance. Figure 56, U.S. Geological Survey Bulletin 1508.
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