The Geologic Story of Colorado National Monument: Revised EditionLohman, Stanley William
Science
The Geologic Story of Colorado National Monument: Revised Edition
Lohman, Stanley William
Colorado National Monument (Colo.); Geology -- Colorado -- Colorado National Monument
Wupatki N.M. near Flagstaff, Ariz., stars the Triassic Moenkopi
Formation. Petrified Forest N.P. (which now includes part of the Painted
Desert) has but one star—the Triassic Chinle Formation, in which are
found many petrified logs and stumps of ancient trees. The
Triassic-Jurassic Glen Canyon Group, which includes the Triassic Wingate
Sandstone, the Triassic(?) Kayenta Formation, and the
Triassic(?)-Jurassic Navajo Sandstone, receives top billing in recently
enlarged Capitol Reef N.P., but the Triassic Moenkopi and Chinle
Formations enjoy supporting roles.
The Triassic(?)-Jurassic Navajo Sandstone, which has a supporting role
in Arches N.P., is the undisputed star of Zion N.P., Rainbow Bridge
N.M., and Glen Canyon National Recreation Area. The Navajo also forms
the impressive reef at the east edge of the beautiful San Rafael Swell,
a dome, or closed anticline, now crossed by Highway I-70 between Green
River and Fremont Junction, Utah.
As we journey upward in the time spiral (fig. 61), we come to the
Jurassic Entrada Sandstone, which stars in Arches N.P., with help from
the underlying Navajo Sandstone, and a supporting cast of both older and
younger rocks. The Entrada also forms the grotesque erosion forms called
“hoodoos and goblins” in Goblin Valley State Park, north of Hanksville,
Utah.
Moving ever upward in the spiral, we come to the Cretaceous—the age of
the starring Mesaverde Group, in which the caves of Mesaverde N.P. were
formed, and which now house beautifully preserved ruins once occupied by
the Anasazi (the ancient people who once dwelt in many parts of the
Plateau).
This brings us up to the Tertiary Period, during the early part of which
the pink limestones and shales of the Paleocene and Eocene Wasatch
Formation were laid down in inland basins. Beautifully sculptured
cliffs, pinnacles, and caves of the Wasatch star in Bryce Canyon N.P.
and in nearby Cedar Breaks N.M. This concludes our climb up the time
spiral, except for Quaternary volcanos and some older volcanic features
at Sunset Crater N.M., near Flagstaff, Ariz.
Thus, one way or another, many rock units formed during the last couple
of billion years have performed on the stage of the Colorado Plateau
and, hamlike, still lurk in the wings eagerly awaiting your applause to
recall them to the footlights. Do not let them down—visit and enjoy the
national parks and monuments of the Plateau, for they probably are the
greatest collection of scenic wonderlands in the world.
Acknowledgments
Public-domain text, read in full here on John Shaqi.
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