A typology of sculpted forms in open bedrock channels / Типология скульптурных форм коренных пород в открытых руслах

Erosional sculpted forms from open bedrock channels in a variety of lithologies are described, classified, and illustrated. The resulting typology demonstrates both the diversity of bedforms in bedrock channels and the existence of features common to many channels and lithologies. This investigation develops a consistent nomenclature and places the study of bedforms in bedrock channels on a rational foundation along with that of their sedimentary counterparts. Four general principles applying to the development of sculpted forms are identified: (1) the continuity of form between endmember types; (2) the convergence of form toward “preferred” morphologies; (3) the constructive interference of the flow structures of contiguous bedforms; (4) the tendency toward the development of sharp transverse crests in bedrock surfaces. The origins of sharp-crested transverse features, and of sharp edges in sculpted forms in general, are discussed. The use of sculpted forms as indicators of flow patterns, and of the dominant erosion processes active within channels, is examined. It is noted that in channels in silicate rocks with abundant sculpted forms, abrasion by suspended load is the main mechanism of erosion, and that erosion by bedload plays only a minor role. In such channels, lithology per se exerts relatively little influence on the formation of sculpted forms, although structural elements of the substrate do. Substrate structure may influence the style of bedforms and/or inhibit their development. Limestone develops a suite of endemic features, indicative of formation by corrosion. Factors that potentially exert control on the scale of bedforms are discussed.