1. Vadodara Institute of Engineering
Kotambi
Subject :Geotechnics and Applied Geology
Subject Code :( )
Topic: STRUCTURE GEOLOGY
Civil Engineering department
Pathak Yatri
Patel Pratik
Ramani Jignesh
Guided by:
Prof. Dharti Soni

2. contents information of primary and secondary geological structures
study of geological faults, folds, joints, and active faulting.
their origin, type & Egg. consideration.
geological mapping, study of strike and dip using models and numerical problems

3. INFORMATION OF PRIMARY AND SECONDARY GEOLOGICAL STRUCTURES
Primary Structures: Those Which Develop At The Time Of Formation Of The Rocks (E.G. Sedimentary Structures, Some Volcanic Structures.

4. Sedimentary Structures
Volcanic Structures
Sedimentary Structures

5. 2. Secondary Structures:
Which Are Those That Develop In Rocks After Their Formation As A Result Of Their Subjection To external forces.

6. Faults
A fault is a fracture in the earth's rock units along which there has been an observable amount of movement and displacement. Unlike folds which form predominantly by compressional stress, faults result from either tension, compression or shear.  

7. Classification of Faults
On the basis of the apparent movement of the fault blocks
On the basis of the amount of the dip of the fault
On the basis of the attitude of the fault
On the basis of the direction of the net slip
On the basis of their mode of occurance

8. On the basis of the apparent movement of the fault blocks
Normal fault
Thrust fault (Reverse Fault)

9. Normal Fault
A Normal Fault Is One In Which The Hanging Wall Has Apparently Moved Down With Respect To The Foot Wall, As Shown In Fig The General Effect Of A Normal Fault On The Beds Is To Pull Apart Or Extend the Strata.

10. Thrust fault (Reverse Fault)
A Thrust Fault Is The One In Which The Hanging Wall Has Apparently Moved Up With Respect To The Foot Wall, As Shown In Fig . The General Effect Of A Thrust Fault Is To Shorten The Rock Strata.
Thrust Fault, < 45
Overthrust Fault, Dip < 10

11. On the basis of the amount of the dip of the fault
Based Upon The Amount Of Dip Of The Fault , There Are Two Types Of Faults :-
High Angle Faults
Low Angle Faults

12. High angle faults
These are those faults in which the fault plane dips steeply, at angles more than 45 , as generally happens in normal faults.

13. Low angle faults
These are those faults in which the faults plane dips gently, at angles less then 45 , as generally happens in thrust faults.

14. On the basis of the attitude of the fault
On This Basis There Are Three Types Of Fault:-
Strike Fault
Dip Fault
Oblique Fault

15. Strike Fault
A strike fault is that in which the strike direction of the fault plane is parallel to the strike direction of the adjacent beds. i.e. the fault strikes along the strike of the beds.

16. Dip fault
A dip fault is that in which the strike of the fault is normal (perpendicular) to the strike of the adjacent beds.

17. Oblique Fault
An oblique fault is that in which the fault plane strikers obliquely to the adjacent beds, i.e. fault plane strike neither parallely nor normally to the adjacent beds.

18. On the basis of the direction of the net slip of the fault
On This Basis, The Following Fault Are Recognised
Dip Slip Fault
Strike Slip Fault
Oblique Slip Fault

19. DIP SLIP FAULT
STRIKE SLIP FAULT

20. On the basis of their mode of occurrence
Depending on their mode of occurance, the important types of faults are:
Horst and garben
Parallel faults
Radial faults
Enchelon faults
Step faults

21. Horst and garben
A Horst Is A Combination Of Two Normal Faults Occuring In Such A Fashion, That Their Side Blocks Have Moved Down With Respect To The Central Block, Resulting In The Formation Of A Raised Land Mass As Shown In Fig.

23. Parallel faults Radial faults
When a number of faults occuring with same strike and dip, they are called parallel faults
Radial faults
When a group of faults are arranged in a radial manner, they are called radial faults.

25. Enchelon faults a group of faults that overlap one another, are called enchelon faults

26. Step faults This Term Represents A Combination Of Parallal Falts, In Which The Beds Are Thrown Into Step-like Arrangement

27. FOLDS
When a set of horizontal rock layers are subjected to compressive force, undulations or curvatures developed in the rock layers. These bends are called “Folds”. these bends may be upwards or downwards. They are also called flexures or bucking phenomenon of rocks.

28. Classification of folds
Classification based on upward or downward bending
Classification based on position of the axial plane
Classification based on degree of compression
Classification based on mode of occurance
Classification based on position of fold axis
Classification based on behaviour with width
Miscellaneous folds

29. Classification based on upward or downward bending
On The Basis Of Upward Or Downward Bending,the Folds Are Classified As :-
Anticlines
Synclines

30. Anticline :-
When The Beds Are Bent Upwards, Into An Arch-like Structure, It Is Calle Anticline fold. In such folds, the beds on either side are inclined away form the crest. This fold is convex upwards.
Synclines :-
When The Beds Downwards, Into A Trough Like Form, The Structure Is Called Synclines . The Fold Is Convex Downwards.

32. Classification based on position of the axial plane
Based On The Position Of The Axial Plane, The Following Types Of Folds Are Recognized :-
Symmetrical Folds
Asymmetrical Folds
Overturned Fold
Recumbent Fold

33. Symmetrical Folds :-
When The Axial Plane Divides A Fold Into Two Equal Halves In Such A Way That One Half Is The Mirror Image Of Another, Then Such A Fold Is Called A Symmetrical Folds.
Asymmetrical Folds :-
The Fold In Which Axial Plane Is Not Vertical But Inclined Is Called Asymmetrical Folds.

35. Overturned Fold :-
An Overturned Fold Is A Severely Folded Fold, In Which The Axial Plane Gets So Much Inclined That The Two Limbs Of The Fold Dip In The Same General Direction. In Such Folds, The Folding Is So Severe That One Of The Two Limbs Come To Occupy The Present Upside Down Position, After Having Suffered A Rotation Through More Than 90. This Limb Is Called The Reversed Limber Overturned Limb Or Inverted Limb.

37. Recumbent Folds :-
These Are Extreme Types Of Overturned Folds, In Which The Axial Plane Acquires An Almost Horizontal Position. In Such Folds, One Limb Lies Vertically Above The Other. The Overlying Limb Is Called Normal Limb, Which The Underlying Limb Is Called Inverted Limb.

39. Classification based on degree of compression
Based on degree of compression, the folds are named as :
Open folds
Closed folds

40. Open Folds :-
When The Layers Of Rock Are Compressed To A Lesser Extent, The Rock Layers May Not Undergo Any Variation In Thickness Of Beds. Such Type Of Folds Are Called Open Folds.

41. Closed Folds :-
In Case Of Severe Compression, The Beds May Get Thinner At The Limbs And Thicker At Crests And Troughs, I.E. Thickness Of Limbs Are Not Uniform, Such Type Of Folds Are Called Closed Folds.

42. Classification based on mode of occurance
Based on the mode of occurance the folds are named as :
Anticlinorium and synclinorium
Dome and basin

43. Anticlinorium and synclinorium :-
when the limbs of folds are not plain but characterized by the appearance of other minor folds on them, the major folds are cold Anticlinorium and synclinorium.

45. Dome and basin :-
a dome is a special of anticline in which the beds dipaway form central point in all directions as shown in fig.
a basin is a special type of syncline in which the beds dip towards the central point, form all direction as shown in fig.

47. Classification based on position of fold axis
Based On The Position Of The Axis Of Fold, The Types Of Folds Are :
Plunging folds
Non- Plunging folds

48. Plunging Folds :-
Any Folds In Which The Axis Of Fold Is Not Horizontal, I.E. It Makes An Angle With The Horizontal Is Called Plunging Fold. It May Be Plunging Anticline Or Syncline.
Non-plunging Folds :-
Any Folds In Which The Axis Of Fold Is Essentially Horizontal, Is Called Non- Plunging Fold.

49. Classification based on behaviour with width
Based on behaviour with width, there are three types of folds :
Similar folds
Parallel folds
Supratenuous folds

50. Similar Folds :-
Similar Folds Are Those In Which The Shapes Of The Shapes Of The Folds Remain The Same With Any Amount Of Depth. In Such Folds, However, Thickness At Troughs And Crests Is More While Thickness Of The Limbs Is Less. Such Type Of Folding Involves The Plastic Movement Of Material Form The Limbs To The Axial Regions , And Hence Are Characteristic Of Zone Rock Flowage.

51. Parallel Folds :-
Parallel Folds Are Those In Which The Shape Of The Folds Varies With Depth, But The Thickness Of The Folded Bed Layers Remains More Or Less The Same . In Such Folds, The Anticlines Become Sharper With Depth, Whereas The Synclines Becomes Broader With Depth.

52. Supratenuous folds :-
these folds exhibit thinning and thickening at the crests and troughs respectively. In such folds, therefore anticline ridges will be thinner due to erosion or lesser deposition of sediments and syncline troughs would be thicker due to large scale accumulation of sediments.

53. Miscellaneous folds Monocline :-
Monocline Is A Local Warping In Which The Horizontal Strata, Exhibit An Abruptly Steep Inclination. This Inclination Of A Monocline May Sometimes Become Vertical.

54. Homocline :-
A Homocline Actually Expresses A Sequence Of Strata Dipping In The Same Direction, At A Uniform Angle

55. Drag folds :-
drag folds are the minor folds devloped within the body of a weaker bed enclosed between two stronger beds. Such folds are developed due to the dragging effects, when stronger beds happer to slide past the sandwitched weaker bed, in opposite directions, during any major folding operations.

57. Chevron folds :-
mostly, the folds are rounded along their axial parts. However, sometimes when the axial parts are not rounded and remain pointed, than they are called chevron fold.

59. Joints
When rock masses are subjected to tensional or compressional forces, regular or irregular fractures devlop in them. Such fractures along which there has been no relative displacement are called ‘joint’.

60. Classification of joints
Classification based on attitude and geometry
Classification based on genesis (origin)

61. Classification based on attitude and geometry
Strike joint
Dip joint
Oblique joint
Strike joint:-
Strike joint are those in which the strike of the joints is parallel to the strike of the beds.

62. Dip joint :-
Dip joints are those in which the strike of the joints is perpendicular to the strike of the beds.
Oblique joint :-
Oblique joints are those in which the strike of the joints in neither parallel nor normal to the strike of the beds.

63. Classification based on genesis (origin)
Tension Joints
Shear Joints
Tension Joints :-
Tension Joints Are Those Which Are Formed Due To Tensile Forces Or Stresses Produced In The Rocks, Either During Their Formation Or After Their Formation. The Direction Of Such Joints Is Always Perpendicular To That Of The Force Which Tries To Pull Them Apart.

65. GEOLOGICAL CROSS SECTION
For understanding the structure of region, geological cross sections are constructed. They are drawn from geological maps along certain given lines. These sections represent the conditions which are to be found at depth.

66. The factors which help in constructing the geological sections are:
1. Contour lines:
These help in drawing topographic profile along the line of section.
2. Structural attitude of strata:
It is inclined by the component of dip computed along the line of c/s.
Thickness of each formation:
This may be obtained from the drill hole records or computed with the help of scale of map, width of outcrop and the dip.

67. Types of geological cross sections:
Normal sections
Oblique sections
The steps involved in the construction of a geological cross sections:
Drawing a topographic profile
Determination of dip and strike
Filling of geological details

68. Normal sections:- Oblique sections:
sections made in the direction normal to the strike are called normal.
Oblique sections:
The sections which are constructed in the direction oblique to the strike are called oblique sections.

69. THANK YOU....