Structural Geology and the Interpretation of Geological Maps 6. With the aid of
ID: 295065 • Letter: S
Question
Structural Geology and the Interpretation of Geological Maps
6. With the aid of annotated diagrams, describe what is meant by the term “lines of no finite longitudinal strain”. Use your description to explain the patterns of shortening and extension within the finite strain ellipse and how boudinaged folds may arise from a single progressive deformation.
7. With the aid of annotated diagrams, explain the similarities and differences between plane strain pure shear and plane strain simple shear deformations.
8. With the aid of annotated diagrams, describe the origins of linear and planar fabrics in rocks using a simple strain models.
9. With the aid of annotated diagrams and field examples, describe the characteristics of the following kinematic models of folding:
(a) orthogonal flexure;
(b) flexural shear;
(c) passive shear;
(d) superimposed homogeneous strain.
10. With the aid of annotated diagrams, define plane strain simple shear and describe:
(a) the pattern of finite strain within ductile shear zones;
(b) a method by which the total displacement across a simple shear zone may be determined;
(c) the re - orientation of cross-cutting linear traces in simple shear zones.
11. (a) For two superimposed strains, show how the finite or total strain is
dependent not only on the strains but also the sequence of superposition.
(b) With the aid of annotated diagrams, describe the formation of:
(i) a structure formed by progressive deformation;
(ii) a structure produced by strain superposition.
Explanation / Answer
6. The intersection points are formed by the concentrical super imposition of the finite strain ellipse on the unstrained cycle . these intersection points are four in number. there wont be any change in the net length for the lines which are joining the opposing points. and these lines are known as the lines of no finite longitudinal strain.