Styles Of Folding

PrefaceAcknowledgementsChapter 1. Mechanisms and Mechanics of Folding Introduction Mechanisms of folding Willis Van Hise De Sitter Carey Ramberg Paterson and Weiss Ghosh Biot Chapple and Spang Mechanics of folding Single-layer folds — low amplitude Single-layer folds — high amplitude Multilayer folds References for Chapters 1, 10 and 11 20Chapter 2. Folding of Bedded Sandstones of the Carmel Formation, Arches National Monument, Utah Summary Introduction Crenulations within Carmel at Arches National Monument Origins of crenulations Sources of shortening of Carmel Areal extent of crenulations in Carmel Conditions of Carmel at time of folding Analysis of fold patterns within Carmel Formation General conditions of rocks Biot theory of buckling of multilayers Differential equation of deflection of multilayer Elastic constants of multilayer Review of assumptions Buckling of multilayer between rigid boundaries Comparison of theoretical folds with folds in the Carmel Formation Effects of irregularities of bedding on folding Reason maximum amplitudes of folds are near base of Carmel Extension of folding into lower part of Entrada References Appendix to Chapter 2Chapter 3. Idealized Fold Forms and Lines of Discontinuity (“Part I”) Summary Introduction Forms of some natural folds Theoretical characteristic directions First-order equations Higher-order equations Linear elasticity theory Nonlinear elasticity theory Lines of discontinuity in ideal folds Lines of apparent discontinuity in natural and experimental folds Some natural folds Some experimental folds Acknowledgment ReferencesChapter 4. Initial Stress and Nonlinear Equations of Equilibrium (“Part II”) Summary Introduction Nonlinear equations of equilibrium Stress boundary conditions Initial and incremental stresses Linearized equilibrium equations and boundary conditions Discussion Acknowledgement ReferencesChapter 5. Transition from Sinusoidal to Concentric-Line to Chevron Folds (“Part III”) Summary Introduction Buckling of isolated, homogeneous layers Solution Experiments Analysis of experiments Generalized solutions for multilayered bodies Folding of a homogeneous stiff layer in a soft medium Folding of elastic multilayers Experimental Theoretical wavelengths of sinusoidal folds Variations of wavelengths within multilayers An explanation for the transition from sinusoidal to concentric-like to chevron folds Discussion Acknowledgement ReferencesChapter 6. Sinusoidal and Reverse Conjugate Kink Folds (Part IV”) Summary Introduction Experiments Interbedded gelatin and rubber Grease between rubber layers Layers with frictional contacts Theory Sinusoidal folding of multilayer between rigid confining media Kink form Criteria for kink folding and sinusoidal folding Widths of kink bands An explanation for sinusoidal and kink folding of multilayers confined by rigid boundaries Sinusoidal form Kink form Acknowledgement ReferencesChapter 7. Asymmetric Folding in Interbedded Chert and Shale of the Franciscan Complex (“Part V”) Summary Introduction Forms of folds in the Franciscan cherts and shales Theory Experiments with elastic multilayers Relatively high interlayer contact strength Low interlayer contact strength Analysis of superimposed shear Analysis of folds in interbedded chert and shale Acknowledgement ReferencesChapter 8. Asymmetric Folding and Monoclinal Kinking (“Part VI”) Summary Introduction Experiments Theory Sinusoidal folding of interbedded stiff and soft layers subjected to layer-parallel shear Elementary theory of monoclinal kink folding Kinking as a process of yielding instability Experiments by Gay and Weiss Spacing of monoclinal kink bands Effect of cohesive strength and pore pressure on kinking Propagation of kink bands Summary of kinking processes and conditions of asymmetric folding Acknowledgement ReferencesChapter 9. Development of Concentric-Line and Chevron Folds and Doubly Plunging Folds in Tertiary Rocks in Part of Coast Ranges, California (“Part VII”) Summary Introduction The Huasna syncline Regional geologic setting Form of the Huasna syncline Times of folding Folds near south end of Huasna syncline Rock units at south end of Huasna syncline Forms of the folds Field evidence for shear in folded rocks Analysis of folds at south end of Huasna syncline Ramberg wavelength for multilayer in confining media Simultaneous folding at different scales Folds in riverbank exposure Significance of the ratio of stress to elastic modulus Folds at The Eagle Larger folds Development of doubly plunging folds Reaction of infinite medium Folding of single layer within soft media Folding of multilayer with zero contact strength Acknowledgement ReferencesChapter 10. Folding of Linear Elastic and Power-Law Materials and Revision of Linearized Theory Introduction Folding of linear elastic materials Equilibrium and rheological equations Boundary conditions Sinusoidal solutions Elimination of special assumptions in linearized theory Sequence of plane-strain deformations Initial stress state Incremental stresses for incompressible materials Equilibrium equations Boundary conditions Comparison of predictions of wavelengths in single layers Comparison of Biot's theory with linearized theory of incompressible Mooney material Comparison of wavelengths predicted by Biot, Ramberg, Fletcher and linearized theories Folding of power-law material with memory Stress—strain relations to first order Equilibrium equations General, sinusoidal solution Approximate, thin-plate solution — single layer Approximate, thin-plate solution — multilayer Preliminary evaluation of single-layer and multilayer folding of rock with memory Appendix Invariants Incremental stresses for compressible materials Relations for initially perturbed boundariesChapter 11. Synthesis Introduction Mechanisms of folding Anisotropy due to interlayering of stiff and soft materials or to slip at contacts between layers Anisotropy due to initial stresses and strains Yielding within layers Yielding between layers Superimposed strain Instabilities Mechanics of folding of materials with memory Folding of incompressible elastic material Elementary theory of sinusoidal folding of multilayers Folding of power-law material Transformation from sinusoidal to concentric-like to chevron folds Theory of kink folding Criteria of kink folding Transformation from sinusoidal to conjugate kink to chevron folds Asymmetric folding Doubly plunging foldsAuthor IndexSubject Index