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Evolution of Drag Folds

Published online by Cambridge University Press:  01 May 2009

Hans Ramberg
Hans Ramberg
Affiliation:
Mineralogisk-Geologisk Institutionen, Uppsala Universitet, Uppsala, Sweden.
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Abstract

Theory and experiments show that a component of compressive strain parallel to layering is necessary to develop drag folds. The component of shear strain needed for the monoclinic symmetry of such folds is not sufficient to form the wavy pattern. Based upon fluid dynamic theory and experiments with layered rubber slabs it is suggested that drag folds on flanks of major folds generally evolve as follows: Layer-parallel compression of more or less straight layered rocks causes some layers to shorten essentially by more or less uniform compressive strain and thickening (thick and not-so-competent layers), other layers to shorten essentially by buckling (thin and most component layers). In the course of time, however, the rate of buckling of the thick layers becomes significant relative to the rate of arc-shortening, and the thin layers with the early formed short buckles are forced to mimic the larger folds of the thick layers more or less passively. In this process the early formed short buckles become tilted and assume the typical drag-fold shape.

Type
Articles
Information
Geological Magazine , Volume 100 , Issue 2 , April 1963 , pp. 97 - 106
Copyright
Copyright © Cambridge University Press 1963

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References

REFERENCES

Billings, M. P., 1954. Structural Geology. New York.Google Scholar
Biot, M. A., 1957. Folding instability of a layered viscoelastic medium under compression. Proc. roy. Soc. Lond., A, 242, 444–54.Google Scholar
Biot, M. A., 1961. Theory of folding of stratified viscoelastic media and its implications in tectonics and orogenesis. Bull. geol. Soc. Amer., 72 1595–1670.Google Scholar
DeSitter, L. U., 1959. Structural Geology. New York.Google Scholar
Hills, E. S., 1953. Outline of Structural Geology. London.Google Scholar
Jaeger, J. C., 1956. Elasticity, fracture and flow. London.Google Scholar
Leith, C. K., 1913. Structural Geology. New York.Google Scholar
Nevin, C. M., 1949. Principle of Structural Geology. New York.Google Scholar
Ramberg, H., 1959. Theoretical and experimental studies of ptygmatic folding. Norsk. geol. Tidsskr., 39, 99–151.Google Scholar
Ramberg, H., 1960. Relationships between length of arc and thickness of ptygmatically folded veins. Amer. J. Sci, 258, 36–46.Google Scholar
Ramberg, H., 1962. Contact strain and folding instability in layered rocks. Geol. Rdsch., 51, 405–440.CrossRefGoogle Scholar
Ramberg, H., (In Press.) Fluid mechanics of viscous buckling applicable to folding of layered rocks. Bull. Amer. Ass. Petrol. Geol., 1963.Google Scholar
Williams, E., 1961. The deformation of confined incompetent layers in folding. Geol. Mag., 98, 317–323.Google Scholar