Note 11 — Early History of the Region

Many of the cliff faces of the Wingate Sandstone, and in parts of the Plateau other sandstones also, are darkened or blackened by desert varnish, a natural pigment of iron and manganese oxides, silica, and clay. (See fig. 32.) The varnish is darker on cliff faces that have been standing longer. The prehistoric inhabitants of the canyon country learned that effective and enduring designs could be created simply by chiseling through the thin dark layer to reveal the buff, tan, or pink sandstone beneath. These petroglyphs were chiseled when the rock face was vertical; afterwards the slab fell to a horizontal position.