Monday, December 3, 2012

Sandstones of the Utah-Arizona Borderlands

About 50 years ago, W. Rex Brown was amazed by evocative patterns and “pictures” he noticed in sandstone near his hometown of Kanab, Utah. As many have observed since, the designs seem to mimic the landscape all around Kanab, which is the famed red-rock country of the Colorado Plateau along the Utah-Arizona border. The region is home to such national parks and monuments as Grand Canyon, Zion, Bryce Canyon and Grand Staircase-Escalante – all within striking distance of Kanab. When cut into slabs large and small, the images on the quarried stone evoke Colorado Plateau landscapes that appear to be decorated with ridges, buttes, pinnacles, valleys and eroded swirls (top photo). Brown and a partner subsequently formed Western Hills Rock & Gem Inc. to market “nature’s most beautiful paintings” as “Kanab Wonderstone,” “Kanab Goldenstone” and “Arizona Sierra,” quarried in both Utah and Arizona. The photo at bottom shows the natural design of a cut boulder outside of the shop. Large pieces of sandstone are mounted on walls in the Kanab shop. Some are framed. Smaller stones have been transformed into clocks, paperweights, picture frames and figurines, such as howling coyotes. Occasionally slabs are painted by artists, who may insert barns, roads and fence lines, adding a pastoral effect to Nature’s gritty canvas. For most of the artful stones, what you see is what you get, but in a few cases, as with Arizona Sierra, the rock is treated with heat to bring out richer, terra cotta tints.

According to postings in the Western Hills Shop, picture sandstone is actually part of the Shinarump Formation, laid down 180 million to 220 million years ago by water and wind. The U.S. Geological Survey describes the Shinarump as a basal conglomerate and pebbly sandstone member of the more extensive Chinle Formation, formed during the Late Triassic. The colors and designs within the rock are created by iron oxides, which filtered into the porous rock from mineral springs. Photo taken on November 7, 2012. Photo details: TOP - Camera Maker: NIKON CORPORATION; Camera Model: NIKON D60; Focal Length: 35.0mm; Aperture: f/5.3; Exposure Time: 0.033 s (1/30); ISO equiv: 400; Exposure Bias: none; Metering Mode: Matrix; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: QuickTime 7.6.4. Bottom - Same except Focal Length: 20.0mm; Aperture: f/9.0; Exposure Time: 0.013 s (1/80); ISO equiv: 200.

Earth Science Picture of The Day

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