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Table of Contents - Special Paper 392A Typology of Sculpted Forms in Open Bedrock Channelsby Keith Richardson and Paul Anthony Carling |
Abstract | 1 | ||
Introduction | 1 | ||
General Remarks on Bedforms in Open Bedrock Channels | 3 | ||
Terminology and Definitions |
5 |
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Introduction | 5 | ||
Erosion Mechanisms | 5 | ||
A Definition of Bedforms in Open Bedrock Channels | 6 | ||
Describing the Effect of Rock Structure on Channel Morphology | 7 | ||
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Structural versus Hydrodynamic Control of Morphology | 7 |
Structurally Influenced Channel Morphologies | 9 | ||
Further Definitions | 10 | ||
Simple, Compound, and Coalesced Forms | 10 | ||
Isolate and Conjugate Forms | 11 | ||
Sharp or Cuspate Edges | 12 | ||
Flutes and Scallops | 12 | ||
Furrows, Grooves, Runnels, Troughs, Welts, and Channels | 13 | ||
Potholes | 14 | ||
A Typology of Bedrock Bedforms |
14 |
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Introduction | 14 | ||
1. Concave Features | 18 | ||
1.1 Potholes | 18 | ||
1.2 Longitudinal Furrows | 29 | ||
1.3 Nonlongitudinal Furrows | 43 | ||
1.4 Furrow Complexes | 46 | ||
1.5 Overhanging Concave Features | 48 | ||
1.6 Shallow Concave Surfaces | 50 | ||
2. Convex and Undulating Surfaces | 50 | ||
2.1 Hummocky Forms | 50 | ||
2.2 Other Convex and Undulating Surfaces | 53 | ||
3. Composite Forms | 55 | ||
3.1 Obstacle Marks | 56 | ||
3.2 Hummocky Forms with Linear Depressions | 60 | ||
3.3 Convex Surfaces with Steep Lee Faces | 63 | ||
4. Solutional Forms | 64 | ||
4.1 Solution Pits and Pans | 64 | ||
4.2 Scallops | 69 | ||
4.3 Other Solutional Forms | 74 | ||
5. Tool Marks | 75 | ||
5.1 Percussion Marks | 75 | ||
5.2 Scratch Marks | 77 | ||
6. Large-Scale Sculpted Features | 78 | ||
6.1 Uniform Bed Gradient | 78 | ||
6.2 Variable Bed Gradient | 79 | ||
Further Observations and Discussion |
83 |
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Principles Applying to the Morphology of Bedrock Bedforms | 83 | ||
1. Continuity of Form | 83 | ||
2. Convergence of Form | 84 | ||
3. The Constructive Interference of the Flow Structures of Contiguous Bedforms | 85 | ||
4. The Prevalence of Sharp Transverse Crests | 86 | ||
The Origin of Two Types of Sharp-Crested Transverse Features | 87 | ||
Sharp-Crested Hummocky Forms and Scallops: A Comparison | 87 | ||
The Origin of Scallops | 87 | ||
The Evolution of Directional Scallop Planforms | 90 | ||
The Origin of Sharp-Crested Hummocky Forms | 90 | ||
The Development of Sharp Edges in General | 92 | ||
The Phenomenon of Sharp Edges in Bedrock Bedforms | 92 | ||
A Criterion for the Development of Sharp Edges | 93 | ||
Types of Sharp Edges | 93 | ||
Mean Flow Pathlines Associated with Active Sharp Edges | 95 | ||
Further Comments on the Interpretation of Bedforms in Open Bedrock Channels | 97 | ||
Bedforms as Indicators of Flow Patterns | 97 | ||
Bedforms as Indicators of the Relative Roles of Bedload and Suspended Load in Erosion | 99 | ||
The Relative Importance of Erosion by Suspended Load and Bedload: A Hypothesis | 101 | ||
The Influence of Substrate on Bedform Development in Open Bedrock Channels | 102 | ||
Bedforms in Carbonate Rocks | 102 | ||
Bedforms in Silicate Rocks | 102 | ||
The Scale of Bedforms in Open Bedrock Channels | 103 | ||
Conclusions |
104 |
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Acknowledgments | 105 | ||
References Cited | 105 |