FUNDAMENTAL OF STRUCTURAL GEOLOGY PRACTICAL

1. What is a strike line ?
Strike lines of a single plane are mutually parallel.
Successive strike lines of equal interval (500 m, 400 m,
300 m, etc.) are equidistant from each other. Steeper
planes produce more close-spaced strike lines.
What is Stratum Contour?
stratum contours are the orthographic/map projection of
strike lines on a horizontal surface.

20. On the map, a fold is generally recognized by symmetrical
repetition of beds (Billings, 1954; Ghosh, 1993; Fossen, 2016)

24. General way to distinguish the folded and unfolded litho-contacts on the map.
A. Litho-contacts separating the litho units P, Q, R crop out in a way that a dark blue line
joining the hinges of the contour Vs and outcrop Vs (almost) coincides. This indicates the
unfolded nature of the litho-contacts.

25. B. Here a line joining the hinges of the contour Vs (red broken line) and that of
the outcrop Vs (green broken line) are away from each other. This indicates
that the litho-contacts are folded. A’. Strike lines drawn for case A.