The Chinle Group - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 129

and has the world's largest concentration
of petrified wood from the Triassic Period
( 131, 132 ). Human history in the area,
which includes the region known as the
Painted Desert, goes back more than 2,000
years, but the earliest historic reports of
petrified wood in this area were made by
US Army Officer, Lieutenant Simpson, in
1849, who discovered fragments near the
present day Canyon de Chelly National

Monument in northeastern Arizona.
Further discoveries were made in the 1850s
in the region south of the present-day
Petrified Forest National Park.
The influx of tourists at the end of the
nineteenth century, resulting from the
building of the transcontinental railroad,
resulted in much removal of the fossil
wood for souvenirs and also in various
commercial ventures. The Arizona

131

131 Petrified Forest National
Park, showing concentrations
of petrified logs on desert
floor.

132

132 Petrified Forest National
Park. Petrified logs are so
common that they are used as
a building material.