Still later in the Triassic Period the Monument became part of a vast
desert. Winds blowing from the northwest brought great quantities of
fine sand and piled them up into large dunes like those in the Sahara or
in Great Sand Dunes National Monument in Colorado. But like all deserts,
it was not always dry—occasional rainstorms produced many small lakes
and ponds. Some of the sand was washed into these lakes or ponds and
settled in level layers. This huge sandpile eventually hardened into the
buff and light-red sandstone that we now know as the Wingate. The shapes
of the old dunes are indicated by the steep dips of sand layers, called
crossbeds, which stand out in sharp contrast to the nearly level layers
formed in the lakes and ponds (fig. 10).
The spectacular scenery of Colorado National Monument owes its existence
largely to the 350-foot cliffs of the Wingate Sandstone (fig. 6) and to
the desert climate, which allows us to see virtually every foot of the
vividly colored rocks and has made possible the creation and
preservation of such a wide variety of fantastic sculptures. A wetter
climate would have produced a far different and smoother landscape in
which most of the rocks and land forms would have been hidden by
vegetation.
Eroded remnants of the Wingate form most of the named rock features of
the Monument and are shown in many of the photographs. Independence
Monument—a towering slab of sandstone that resembles a bridge pier (fig.
6)—is all that is left of a high narrow wall that once connected the
point east of Independence View with the high mesa north of the slab and
which once separated the two entrances of Monument Canyon. In a few
thousand years this remnant, too, may be gone.
Vertical cliffs and shafts of the Wingate Sandstone endure only where
the top of the formation is capped by beds of the next younger rock
unit—the Kayenta Formation. The Kayenta is much more resistant to
erosion than the Wingate, so even a few feet of the Kayenta, such as the
cap on top of Independence Monument, protect the rock beneath. Once this
cap has been eroded away, the underlying Wingate weathers into rounded
domes, such as the Coke Ovens.
Cold Shivers Point (fig. 53)—a toadstool shaped cap of sandstone of the
Kayenta above a vertical cliff of the Wingate—is perhaps the most aptly
titled feature of the Monument.
[Illustration: PETRIFIED SAND DUNES in Wingate Sandstone along old
Serpents Trail. Looking north across The Redlands and Grand Valley
to the Book Cliffs. Battlement Mesa on right skyline. (Fig. 10)]
The Coke Ovens (fig. 11) and Squaw Fingers were formed partly because
most of the caprock of Kayenta has been weathered away and also because
the brittle rocks were cracked along an evenly spaced set of vertical
joints. These joints trend northward between the two named features.
More rapid weathering along these joints helped form the separate
rounded domes or spires between them. Similarly, northwestward-trending
vertical joints connect and helped shape Kissing Couple, Pipe Organ, and
Sentinal Spire.
[Illustration: THE COKE OVENS, looking north from overlook beneath
Artists Point. A set of north-south joints has allowed erosion of
the Wingate Sandstone to proceed more rapidly along these zones of
weakness and has helped create the four ovens shown. Weathering away
of the protective caprock of the overlying Kayenta Formation has
produced rounded tops on all but the left-hand shaft, which is still
protected by the Kayenta. Note alcoves and arches in cliff of the
Wingate beyond, the formation of the one on the right having been
aided by removal of the underlying soft Chinle Formation. Bench
covered by piñon and juniper above Wingate is resistant thin-bedded
Kayenta Formation. Cliff above the bench is the Slick Rock Member of
the Entrada Sandstone. The Coke Ovens were named from their
resemblance to the beehive-shaped brick ovens formerly used to
convert bituminous coal into coke for smelting iron. (Fig. 11)]
Many of the cliff walls of the Wingate are vertical, some even overhang,
yet in some places the slopes are gentle enough to hold talus and to be
climbed (fig. 12). Why is this? The answer to this question is given in
a later section on “Canyon Cutting.”
Arches or shallow caves weathered out of some cliff faces of the
Wingate, particularly where the underlying Chinle Formation has been
partly scoured away. Although there are no large caves within the
Monument, there are three in a row along the road 3 miles west of the
Glade Park Post Office. One of these was inhabited until 1958 (fig. 5).
Many of the cliff faces of the Wingate are darkened or blackened by
desert varnish—a natural pigment of iron and manganese oxides, silica,
and clay.[19]
Dinosaurs left their footprints in the sands of the Wingate in parts of
the Colorado Plateau, but no tracks or fossils have yet been found in
this formation in or near the Monument.