The influence of sandstone caprock material on bedrock channel steepness within a tectonically passive setting: Buffalo National River Basin, Arkansas, USA

Bedrock channel profile analysis typically assumes that channels evolve toward a condition of topographic steady state where channel morphology is adjusted to rock erodibility, uplift rates, and stream power. Here we use the integral method of channel profile analysis to quantify channel steepness w...

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Bibliographic Details
Published in:Journal of geophysical research. Earth surface 2016-09, Vol.121 (9), p.1635-1650
Main Authors: Thaler, E. A., Covington, M. D.
Format: Article
Language:English
Subjects:
Bedrock
bedrock channels
Boulders
Channel morphology
Channels
Constraining
Freshwater
integral method
Lithology
normalized steepness
Ozark Mountains
Plate tectonics
River basins
Rivers
Rocks
Sandstone
sandstone caprock
Statistical analysis
Steepness
Topography
Tributaries
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Summary:Bedrock channel profile analysis typically assumes that channels evolve toward a condition of topographic steady state where channel morphology is adjusted to rock erodibility, uplift rates, and stream power. Here we use the integral method of channel profile analysis to quantify channel steepness within a large set of tributary channels that incise through layered rocks in the Buffalo National River Basin in northern Arkansas. Statistical analysis of these channels demonstrates that normalized channel steepness is not a function of local bedrock lithology but is influenced by coarse sediment supply. Specifically, normalized steepness is greatest in reaches of the basin where an interval of Pennsylvanian sandstone forms a caprock on the ridges. Block detachment of the sandstone causes large boulders to be stranded in the upper tributaries where stream power is too low to mobilize or effectively erode the boulders. Within these channels, normalized steepness is correlated with sandstone boulder size and percent boulder coverage rather than local lithology, despite strong contrasts in the mechanical strength of the lithologies incised. This analysis suggests that removal of caprock material is rate limiting within the landscape and may be responsible for the long‐term persistence of topography within this tectonically passive setting. Key Points Integral method used to investigate normalized steepness in various lithologies Steepness is controlled by presence or absence of caprock rather than lithology Removal of caprock is rate limiting in landscape
ISSN:2169-9003
2169-9011
DOI:10.1002/2015JF003771