Photographers: Ruth Sturby and John Mauel
Summary Authors: John Mauel and Ruth Sturby
The photo above shows a petrified log we discovered in northern Arizona. On our way to Flagstaff in early December 2013 we pulled off Highway 89 in the Navajo Nation south of Page and set up camp after dark. Only by morning light did we see that we had been camping on several nearly parallel petrified logs – the longest were approximately 50 ft (15 m) long and 20 in (50 cm) in diameter. They’re embedded in the Chinle Formation. The Late Triassic Chinle is noted for its petrified logs – it’s the major formation in Petrified Forest National Park. The presence of fine cross-bedded sandstone surrounding the logs (close up at left) suggests that the Chinle here is more fluvial than lacustrine. Though this area is high (4,774 ft or 1,455 m) and dry now, in the Triassic it was low-lying swampy land crisscrossed by slow moving streams lined with a type of conifer (Araucarioxylon arizonicum). Note: If you go to the coordinates below you can see the logs at our campsite.
Photo details: Top - Camera Maker: NIKON; Camera Model: COOLPIX P510; Focal Length: 7.1mm (35mm equivalent: 40mm); Aperture: f/3.3; Exposure Time: 0.010 s (1/100); ISO equiv: 100. Left - Same except: Focal Length: 4.3mm (35mm equivalent: 24mm); Aperture: f/3.0; Exposure Time: 0.013 s (1/80).
