ON BED FORMS AND PALAEOCURRENTS |
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| Authors: | J R L ALLEN |
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| Institution: | Sedimentology Research Laboratory, Department of Geology, University of Reading, Reading (Great Britain) |
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| Abstract: | Bed forms arise by interaction between a fluid flow and the sediment transported over or close to the bed. The geometry of bed forms is two-dimensional or three-dimensional. Two-dimensional bed forms generate two-dimensional internal sedimentary structures and are adjusted to two-dimensional flow-vector fields. Three-dimensional bed forms generate three-dimensional internal sedimentary structures and are adjusted to three-dimensional flow-vector fields. Many shallow-water flow systems observable today are each characterised by flow-vector fields of unequal rank, and hence are hierarchically structured. Hierarchies of bed forms and internal structures which parallel the hierarchies of flow-vector fields can also be established in the case of these flow systems. A single type of bed form or internal structure from an hierarchically structured flow system cannot specify that system fully with regard to either its directional or flow-dynamic characteristics. An approach to palaeocurrent analysis that is more flexible and comprehensive than previously attempted may therefore be desirable. |
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