>That redwall was not fully lithified when the canyon was cut is easily
>ascertainable at a number of sites in the canyon, but most notably on the
>rim of the inner gorge just below O'Neill Butte, where a contorted slab of
>Redwall sits perched on the rim of the inner gorge, frozen in time.
>Apparently the Redwall was undercut in this area, resulting in slope
>failure and a massive slab of the Redwall (about .5 km in diameter and
>maybe 50 ft thick) slid down the Tonto slope toward the gorge where it now
>sits. The nearest cliff of redwall is more than a mile away. The slab
>itself consisting of a few beds was apparently semiconsolidated, because it
>is massively brecciated, but recemented in place. This is clear evidence
>(as are the hundred or so other places in the canyon where the same
>phenomenon can be viewed on a lesser scale) for rapid cutting and erosion
>of the section in the canyon. Other places that attest to rapid erosion
>and massive displacement of the Paleozoic sediments are at Surprise valley
>where a block 5 or 6 miles in length consisting of the entire Paleozoic
>section has slumped into the canyon, and at the mouth of Red Canyon where a
>similar large mass of the column has slumped riverward, although in this
>latter case the fault is along a diabase dike, which may have facilitated
>the process. The river was already deeply entrenched when this occurred,
>as is indicated by the relationship of the slide block to the present gorge.
Fascinating example. Since you have seen this and I haven't, let me ask a
few questions.
How do you distinguish the time of the deformation. In other words could
this be a deformed block of Redwall which subsequently slid down the
mountain. The deformation having taken place long before the slide.
How do you rule out a slope failure which caused brecciation at the time of
the fall and then re-cementation.
I guess I need clarification on whether the deformation you speak of is
WITHIN the various blocks of Redwall or BETWEEN the fragments of the Redwall.
Concerning the slumps into the canyon: Slumps occur along any steep slope.
If an entire section of paleozoic rock slumped into the canyon, I wouldn't
find that surprising. What I would find surprising is internal deformation
of the block which slid--deformation not caused by fracturing but by soft
sediment flow. It is the internal morphology of the blocks which is
important and I can't get that info from what you wrote.
Can you refer me to any articles where I can read about this?
glenn
Adam, Apes, and Anthropology: Finding the Soul of Fossil Man
and
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm