Page 2 - SEG - First issue

Academic Articles

I-STRUCTURE GEOLOGY

Folds are probably the structure that comes to mind when we say the words
(geological structure), so why is the fold such a distinctive term related to
geological structures ...
well folds are waves in stratified rocks, these rocks were once horizontal strata
but they have been buckled...
Folds are usually formed by compressional stress. like any architectural
structure a fold has its terminology which describe it fold terminology :

1- limbs : The generally planar region of a
fold which lies between two adjacent hinge
lines and is confined between the zones of
maximum curvature.
2- inflection point : the point where the
sense of curvature is converted .
3- hinge: place of maximum curvature on
the fold .
4- axes : it is the intersection of the axial
plane with a bed in the fold
5- axial plane : imaginary planar surface
defined by the connection of the hinges and
symmetrically divides the fold .
6- wave length : distance between two
peaks or two troughs
7-median surface : an imaginary surface
connecting adjacent infliction points
8- amplitude : it is the distance form the
median plane to the hinge

Folds are classified according to the attitude of Most famous types of folds
their fold axes which can be called a hinge line if 1- anticline
the fold isn't cylindrical . the axes can be vertical 2- syncline
or inclined and in some cases horizontal like the 3- dome
recumbent fold.
4- basin

1- Anticline is the fold where every limb 2- Syncline is the fold Dome and basin aren't like the typical folds
dips away from the peak where the limbs dip because they have more of a circular plane than
anticlines form one of the most toward the trough
important hydrocarbon trap formations a linear one .
about 80 % of the world's petroleum a synclinorium is a large
was found in anticlines. syncline which has minor 3- The dome is 4- Basin is concave
antiforms are folds that take the shape folds in it
of an anticline but it's younging convex upward upward and the
direction is inverted an anticline should and the strata dip strata dip inward
have the oldest rock in the center . outward towards towards the center
anticlinorium is a large scale anticline the center
with smaller folds inside it

Page 2