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Preservation of Relic Features in the Modern Landscape
How have these canyons been preserved? Why didn’t new drainage channels develop
in response to the change in gradient of the uplifted plateau? It appears that
the most important factor in the preservation of the relic channels is that
which influenced channel location in the beginning ... faults and fractures.
Given the magnitude of faulting and fracturing in the area it is unlikely that
even a catastrophic event or events would or could completely alter the already
established drainage network.5 Working in tectonically similar conditions to
those found on the plateau, Miller and Dunne (1996) observed that in areas of compressional tectonics, mass wasting along surface-parallel or shallowly
dipping fractures tended to preserve valley form over time.6 Burbank, et. al.
(1996) suggested another factor may have contributed to the preservation of the
original pre-uplift channels. Their work found that in most cases, drainage
gradients were unchanged following uplift due to the failure of bedrock-uplift
to keep pace with the rate at which channel valleys were continuing to incise
their underlying bedrock.
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5 Oberlander (1965) observed similar anomalies in his work on the Zagros Streams.
6 Though conducted in a humid environment, Potter (1978) observed similar results. He found that an already established drainage system would not significantly change when unlifted by tectonic reshaping (cf. also Cox, 1989).
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