Section 1Folds on geologic map

Edited by: Mostafa Abdel Azim MasoudDemonstrator – Geology department- Faculty of Science

Synthesis of fold

Types of folds according to attitude of axial plane

Criteria of foldsA) Non-plunging folds (horizontal folds)

• Repetition of strata.

• Inversion of dip direction of strata.

• Common core.

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Criteria of foldsB) Plunging folds ( الطيات(الغاطسة• Repetition of strata.• Inversion of dip direction of strata• Common core.

• Presence of fold closure.

• In the case of plunging anticline folds, the plunge is in the same direction of the closure.

• In the case of plunging syncline folds, the plunge is in the opposite direction of the closure.

Difference between syncline and anticline folds on map1) Direction of strata dipIn anticlines the direction of strata around the axis is away of the core and in syncline the direction is toward the core.

2) The age of strataIn anticlines the oldest strata are in the core and the youngest and vice versa in synclines.

3)Direction of plunge In plunging anticline folds, the plunge is in the same direction of closure, and in synclines, the plunge in opposite direction of closure.

How to describe the folds on map ?1-Type of strata consisting the fold.2-Direction of fold (fold axis).3-Direction of plunge (in case of plunging fold).4-Type of fold:*Symmetrical or non symmetrical.*Plunging or non-plunging.*Syncline , anticline, monocline.

How do you know the direction of river on map• 1) V-shape• 2) Alluvial deposits• 3) Values of contour lines

Report of mapTo write a report for a geologic map, you should keep in mind three aspects which are :1) Geomorphology: such as volcanic activity, erosion, transgression,

regression, general slope ………..etc.2) Structure geology : such as folds, faults, domes, basins,

unconformities…..etc.3) Topography: mountains, hills, plateau……etc.

4) History of map.

Double plunging folds

Double plunging anticline

Map 2

faults