View to the
south-southeast with Saddle Canyon in the lower right corner.
Further downstream Little Nankoweap and Nankoweap Creeks enter
from the right. Nankoweap Creek produces a large delta
(outwash fan) as its drainage taps the easily eroded upper
layers of the Grand Canyon Supergroup.
The topography of the Grand Canyon begins to
change from about Saddle Canyon downstream. The rim on the
east (left) side is still the flattish Kaibab Limestone of the
Marble Platform, but to the west (right), first the
encroachment of the Kaibab Plateau produces an upslope, and
then everything changes dramatically (see below).
View to the
south-southeast with Nankoweap Canyon and its outwash fan in
the foreground. In the middle distance Kwagunt Creek enters
from the right to produce another outwash fan. The Canyon of
the Little Colorado River can be seen left of center at the
top edge. To the right of the Colorado River a small remnant
of the flattish Marble Platform remains on top of Nankoweap
Mesa. Then everything becomes chaotic west (right) of the
The Butte Fault (East Kaibab Monocline) enters
from the lower right edge and then curves upward toward the
top of the picture. Initial movement along this fault some 800
million years ago dropped the strata to the right (west) some
3,000 to 4,000 feet lower than layers to the east. When the
Grand Canyon Supergroup was faulted downward, it was protected
from further surface erosion. Subsequently, the same Paleozoic
layers that form the Marble Canyon section of the Grand Canyon
covered the Supergroup layers.
In the last 70 million years movement along the
fault has been in the opposite direction and the area to the
west of the fault has been uplifted (probably 3 separate
uplifts) to form the Kaibab Plateau. (These uplifts include
doming over a wider area than just the fault zone.) When the
Colorado River established its current route some 5.4 million
years ago, areas closest to the river were subject to the
greatest erosion, and the Paleozoic layers were eroded away.
Once these upper layers were gone, erosion could rapidly erode
the softer Grand Canyon Supergroup. Thus topography to the
right of the fault zone has been eroded down lower than the
few high mesas (e.g. Nankoweap) that are found right next to
the river. The rapid erosion (includes debris flows) of the
soft Supergroup layers feeds the outwash fans (deltas) of
Nankoweap and Kwagunt Creeks.
river miles 40 to 48
to river miles 56 to 64
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