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Folds and faults ppt

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The document provides information about folds and faults. It defines folds as bent or curved rock layers, and describes common fold types like anticlines and synclines. It also defines various fault types including normal faults, thrust faults, strike-slip faults, and oblique faults. Specific structures are described like the San Andreas Fault, which is a major strike-slip fault in California. Dip, strike, heave and throw are also defined in relation to describing the orientation and movement of geological structures.

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PRESENTATION ON FOLDS AND FAULTS ACTIVITY-4 SUBMITTED TO- MR. MANISH BHUTANI SUBMITTED BY- AMAN BHAGAT ROLL NO. 604/18 CIVIL 5TH SEMESTER 1
➢ FOLDS- In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as fold trains). FOLDS 2
▪ TYPES OF FOLDS- • Anticline • Syncline • Monocline • Chevron fold • Recumbent fold • Dome and Basin DIFFERENT TYPES OF FOLDS 3
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of a anticline. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. • ANTICLINE- CROSS- SECTIONAL DIAGRAM OF ANTICLINE 4
DESCRIPTION OF PARTS OF ANTICLINE- Anticlines are usually developed above thrust faults, so any small compression and motion within the inner crust can have large effects on the upper rock stratum. Stresses developed during mountain building or during other tectonic processes can similarly warp or bend bedding and foliation. The shape formed will also be very dependent on the properties and cohesion of the different types of rock within each layer. ANTICLINE FOLDS5
• SYNCLINE- In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline). SYNCLINE FOLDS 6
DESCRIPTION OF PARTS OF SYNCLINE- On a geologic map, synclines are recognized as a sequence of rock layers, with the youngest at the fold's center or hinge and with a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate, the structure is a basin. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. SYNCLINE FOLDS 7
• Monocline- A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence. MONOCLINE FOLDS 8
DESCRIPTION OF PARTS OF MONOCLINE- • By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence. • As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence. • As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence. MONOCLINE FOLDS 9
▪ CHEVRON FOLDS- Chevron folds are a structural feature characterized by repeated well behaved folded beds with straight limbs and sharp hinges. Well developed, these folds develop repeated set of v- shaped beds.They develop in response to regional or local compressive stress. Inter-limb angles are generally 60 degrees or less. Chevron folding preferentially occurs when the bedding regularly alternates between contrasting competences. CHEVRON FOLDS 10
DESCRIPTION OF PARTS OF CHEVRON FOLDS- In response to compressional stress, geological beds fold in order to minimize dissipation of energy. Given an unconstrained bed, folding does so by correspondingly minimizing bending and thus develops a sinusoidal geometry. In a stratigraphic sequence, and physically constrained by their neighbours. Chevron folds are energetically preferred to conventional sinusoidal folds as they minimize ductile flow to the expense of localized bending. CHEVRON FOLDS 11
• Dome and Basin- A dome is a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal- shaped protrusions on the Earth's surface. Consequently, if the top of a dome has been eroded flat, the resulting structure in plan view appears as a bullseye, and each ring growing progressively older moving inwards. DOME AND BASIN FOLDS 12
DESCRIPTION OF PARTS OF CHEVRON FOLDS- Structural domes can be formed by horizontal stresses in a process known as refolding, which involves the superposition, or overprinting, of two- or more fold fabrics. Upright folds formed by a horizontal primary stress in one direction can be altered by another horizontal stress oriented at 90 degrees to the original stress. DOME AND BASIN FOLDS 13
➢ FAULTS- A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. This movement may occur rapidly, the form of an earthquake - or may occur slowly, in the form of creep. Faults may range in length from a few millimeters to thousands of kilometers. Most faults produce repeated displacements over geologic time. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other.14
• Dip slip fault • Oblique fault • Strike slip fault • Listric fault • Ring fault ▪ TYPES OF FAULTS- Different types of faults 15
• Dip slip fault- In a normal fault, the hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is a graben. An upthrown block between two normal faults dipping away from each other is a horst. Low-angle normal faults with regional tectonic significance may be designated detachment faults. Dip slip faults 16
DESCRIPTION OF DIP SLIP FAULT- Flat segments of thrust fault planes are known as flats, and inclined sections of the thrust are known as ramps. Typically, thrust faults move within formations by forming flats and climb up sections with ramps. Faults may be reactivated at a later time with the movement in the opposite direction to the original movement (fault inversion). A normal fault may therefore become a reverse fault and vice versa. 17
• Oblique fault- A fault which has a component of dip-slip and a component of strike-slip is termed an oblique- slip fault. Nearly all faults have some component of both dip- slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. 18
DESCRIPTION OF OBLIQUE FAULT- A fault which has a component of dip-slip and a component of strike-slip is termed an oblique- slip fault. Nearly all faults have some component of both dip-slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional and others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active. OBLIQUE FAULT 19
• Strike slip fault- In a strike-slip fault (also known as a wrench fault, tear fault or transcurrent fault),the fault surface (plane) is usually near vertical, and the footwall moves laterally either left or right with very little vertical motion. Each is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault. 20
DESCRIPTION OF STRIKE SLIP FAULT- A special class of strike-slip fault is the transform fault, when it forms a plate boundary. This class is related to an offset in a spreading center, such as a mid- ocean ridge, or, less common, within continental lithosphere, such as the Dead Sea Transform in the Middle East or the Alpine Fault in New Zealand. Transform faults are also referred to as "conservative" plate boundaries, inasmuch as lithosphere is neither created nor destroyed. STRIKE SLIP FAULT 21
• Listric fault- Listric faults are similar to normal faults but the fault plane curves, the dip being steeper near the surface, then shallower with increased depth. The dip may flatten into a sub-horizontal décollement, resulting in horizontal slip on a horizontal plane. The illustration shows slumping of the hanging wall along a listric fault. Where the hanging wall is absent (such as on a cliff) the footwall may slump in a manner that creates multiple listric faults. Subduction zones are a special class of thrusts that form the largest faults on Earth and give rise to the largest earthquakes. 22
LISTRIC FAULT 23
• Ring fault- Ring faults, also known as caldera faults, are faults that occur within collapsed volcanic calderas and the sites of bolide strikes, such as the Chesapeake Bay impact crater. Ring faults are result of a series of overlapping normal faults, forming a circular outline. Fractures created by ring faults may be filled by ring dikes. Most ring-faults of collapse calderas are either circular or slightly elliptical in plan view, vertical or steeply dipping, and have vertical displacements from several hundred metres to a few kilometres. 24
STRIKE SLIP FAULT 25
➢ SAN ANDREAS FAULT- San Andreas Fault, major fracture of the Earth’s crust in extreme western North America. The fault trends northwest for more than 800 miles (1,300 km) from the northern end of the Gulf of California through western California, U.S., passing seaward into the Pacific Ocean in the vicinity of San Francisco. Tectonic movement along the fault has been associated with occasional large earthquakes originating near the surface along its path, including a disastrous quake in San Francisco in 1906, less serious event there in 1989, and destructive quake centred in the Los Angeles suburb of Northridge in 1994 that occurred along one of the San Andreas’s larger secondary faults. • DESCRIPTION- 26
SAN ANDREAS FAULT • HISTORY- The San Andreas Fault was born about 30 million years ago in California, when the Pacific Plate and the North America plate first met. The new configuration meant the two plates slid past one another instead of crashing into each other, a boundary called a strike-slip fault. 27
Researchers have measured identical rocks offset by 150 miles (241 kilometers) across either side of the fault. For example, the volcanic rocks in Pinnacles National Park south of Monterey match volcanic rocks in Los Angeles County (called the Neenach volcanics). Geologists think the total amount of displacement along the fault is at least 350 miles (563 km) since it formed. • Earthquake prediction- The San Andreas Fault was the site of a massive effort to drill into Earth's crust and investigate a fault at depth. In 2004, work began near the town of Parkfield on the San Andreas Fault Observatory at Depth(SAFOD) to drill nearly 2 miles (3.2 km) into the fault. Parkfield, in central California, pops off a moderate earthquake of around magnitude 6 every couple decades, and is a center for earthquake research. Scientists predicted another earthquake should occur in 1993, but it didn't happen until 2004. Previous quakes hit in 1857, 1881, 1901, 1922, 1934 and 1966. Rocks retrieved from the deep drilling project revealed that slippery clays may be responsible for some of the "creeping" behavior along the San Andreas Fault. 28
➢ DIP AND STIRE- Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25°E for a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25°E would simply be 025), or the azimuth number followed by the degree sign (example of N25°E would be 025°). One technique is to always take the strike so the dip is 90° to the right of the strike, in which case the redundant letter following the dip angle is omitted (right hand rule, or RHR). STIRE AND SIP OF BED 29
➢ HADE AND THROW- Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation (strain) in the rocks, and ultimately, to understand the stress field that resulted in the observed strain and geometries. • HADES- Slip is defined as the relative movement of geological features present on either side of a fault plane. A fault's sense of slip is defined as the relative motion of the rock on each side of the fault with respect to the other side. In measuring the horizontal or vertical separation, the throw of the fault is the vertical component of the separation and the heave of the fault is the horizontal component, as in "Throw up and heave out". • THROW- 30
HADE AND THROW FAULTS 31
➢ PARTS OF FOLDS- In a series of folds it is evident like waves. They consist of alternate crests and troughs. The crest of the fold is termed as anticline while the trough is called synclines. An anticline and syncline constitute a fold. Limbs or Flanks: Limbs or a flank of the fold is sloping side from the crest to the trough. Axial plane: An imaginary plane bisecting the vertical angle between equal slopes on either sides of the crest line. Axis of the fold: The line that divides the section of the fold. 32
• TYPES OF FOLDS- 1. Homocline: Beds dipping in one direction but at the same angle. 2. Monocline: Infect beds, there are steep dip at one or two places. Such a bed where inclination is high at one or two places compared to the rest. Homocline 3. Structural Terrace: A bed, which is inclined in one direction, may become more or less flat at one place. 4. Anticline and Syncline- Anticline is simple fold, which is convex upwards. In Greek it means opposite inclined. In this fold the limbs dip always from each other. Syncline is simple fold, which is concave upwards. In Greek it means together inclined. In this fold the limbs dip towards each other.33
5. Overturned Fold: In this fold the two limbs dip in the same direction but at different angles. The axial plane is inclined. 6. Isoclinal Fold: In Greek Isoclinal fold means the two limbs dip in the same direction but at the same angle. 7. Chevron Fold: Usually the crest and troughs of a fold are rounded, but sometimes the folds are characterised by sharp crests and troughs. Such folds where the crests and troughs are sharp and angular are called Chevron Folds. 8. Recumbent Fold: A fold in which the axial plane is absolutely horizontal and the limbs are also more or less horizontal is called Recumbent Fold as in the accompanying. 9. Drag Fold: These are minor or small folds formed when competent beds (weak beds) moves over the incompetent beds. Drag fold34
10. Anticlinorium and Synclinorium: Anticlinorium and Synclinorium are called respectively to exceptionally large sized fold. Anticline and Syncline when it is composite fold. An Anticlinorium is a fan shaped structure and the trend if the fold is anticline character. 35
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Folds and faults ppt

  • 1. PRESENTATION ON FOLDS AND FAULTS ACTIVITY-4 SUBMITTED TO- MR. MANISH BHUTANI SUBMITTED BY- AMAN BHAGAT ROLL NO. 604/18 CIVIL 5TH SEMESTER 1
  • 2. ➢ FOLDS- In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as fold trains). FOLDS 2
  • 3. ▪ TYPES OF FOLDS- • Anticline • Syncline • Monocline • Chevron fold • Recumbent fold • Dome and Basin DIFFERENT TYPES OF FOLDS 3
  • 4. In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of a anticline. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. • ANTICLINE- CROSS- SECTIONAL DIAGRAM OF ANTICLINE 4
  • 5. DESCRIPTION OF PARTS OF ANTICLINE- Anticlines are usually developed above thrust faults, so any small compression and motion within the inner crust can have large effects on the upper rock stratum. Stresses developed during mountain building or during other tectonic processes can similarly warp or bend bedding and foliation. The shape formed will also be very dependent on the properties and cohesion of the different types of rock within each layer. ANTICLINE FOLDS5
  • 6. • SYNCLINE- In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline). SYNCLINE FOLDS 6
  • 7. DESCRIPTION OF PARTS OF SYNCLINE- On a geologic map, synclines are recognized as a sequence of rock layers, with the youngest at the fold's center or hinge and with a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate, the structure is a basin. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. SYNCLINE FOLDS 7
  • 8. • Monocline- A monocline (or, rarely, a monoform) is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence. MONOCLINE FOLDS 8
  • 9. DESCRIPTION OF PARTS OF MONOCLINE- • By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence. • As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence. • As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence. MONOCLINE FOLDS 9
  • 10. ▪ CHEVRON FOLDS- Chevron folds are a structural feature characterized by repeated well behaved folded beds with straight limbs and sharp hinges. Well developed, these folds develop repeated set of v- shaped beds.They develop in response to regional or local compressive stress. Inter-limb angles are generally 60 degrees or less. Chevron folding preferentially occurs when the bedding regularly alternates between contrasting competences. CHEVRON FOLDS 10
  • 11. DESCRIPTION OF PARTS OF CHEVRON FOLDS- In response to compressional stress, geological beds fold in order to minimize dissipation of energy. Given an unconstrained bed, folding does so by correspondingly minimizing bending and thus develops a sinusoidal geometry. In a stratigraphic sequence, and physically constrained by their neighbours. Chevron folds are energetically preferred to conventional sinusoidal folds as they minimize ductile flow to the expense of localized bending. CHEVRON FOLDS 11
  • 12. • Dome and Basin- A dome is a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal- shaped protrusions on the Earth's surface. Consequently, if the top of a dome has been eroded flat, the resulting structure in plan view appears as a bullseye, and each ring growing progressively older moving inwards. DOME AND BASIN FOLDS 12
  • 13. DESCRIPTION OF PARTS OF CHEVRON FOLDS- Structural domes can be formed by horizontal stresses in a process known as refolding, which involves the superposition, or overprinting, of two- or more fold fabrics. Upright folds formed by a horizontal primary stress in one direction can be altered by another horizontal stress oriented at 90 degrees to the original stress. DOME AND BASIN FOLDS 13
  • 14. ➢ FAULTS- A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. This movement may occur rapidly, the form of an earthquake - or may occur slowly, in the form of creep. Faults may range in length from a few millimeters to thousands of kilometers. Most faults produce repeated displacements over geologic time. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other.14
  • 15. • Dip slip fault • Oblique fault • Strike slip fault • Listric fault • Ring fault ▪ TYPES OF FAULTS- Different types of faults 15
  • 16. • Dip slip fault- In a normal fault, the hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is a graben. An upthrown block between two normal faults dipping away from each other is a horst. Low-angle normal faults with regional tectonic significance may be designated detachment faults. Dip slip faults 16
  • 17. DESCRIPTION OF DIP SLIP FAULT- Flat segments of thrust fault planes are known as flats, and inclined sections of the thrust are known as ramps. Typically, thrust faults move within formations by forming flats and climb up sections with ramps. Faults may be reactivated at a later time with the movement in the opposite direction to the original movement (fault inversion). A normal fault may therefore become a reverse fault and vice versa. 17
  • 18. • Oblique fault- A fault which has a component of dip-slip and a component of strike-slip is termed an oblique- slip fault. Nearly all faults have some component of both dip- slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. 18
  • 19. DESCRIPTION OF OBLIQUE FAULT- A fault which has a component of dip-slip and a component of strike-slip is termed an oblique- slip fault. Nearly all faults have some component of both dip-slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional and others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active. OBLIQUE FAULT 19
  • 20. • Strike slip fault- In a strike-slip fault (also known as a wrench fault, tear fault or transcurrent fault),the fault surface (plane) is usually near vertical, and the footwall moves laterally either left or right with very little vertical motion. Each is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault. 20
  • 21. DESCRIPTION OF STRIKE SLIP FAULT- A special class of strike-slip fault is the transform fault, when it forms a plate boundary. This class is related to an offset in a spreading center, such as a mid- ocean ridge, or, less common, within continental lithosphere, such as the Dead Sea Transform in the Middle East or the Alpine Fault in New Zealand. Transform faults are also referred to as "conservative" plate boundaries, inasmuch as lithosphere is neither created nor destroyed. STRIKE SLIP FAULT 21
  • 22. • Listric fault- Listric faults are similar to normal faults but the fault plane curves, the dip being steeper near the surface, then shallower with increased depth. The dip may flatten into a sub-horizontal décollement, resulting in horizontal slip on a horizontal plane. The illustration shows slumping of the hanging wall along a listric fault. Where the hanging wall is absent (such as on a cliff) the footwall may slump in a manner that creates multiple listric faults. Subduction zones are a special class of thrusts that form the largest faults on Earth and give rise to the largest earthquakes. 22
  • 24. • Ring fault- Ring faults, also known as caldera faults, are faults that occur within collapsed volcanic calderas and the sites of bolide strikes, such as the Chesapeake Bay impact crater. Ring faults are result of a series of overlapping normal faults, forming a circular outline. Fractures created by ring faults may be filled by ring dikes. Most ring-faults of collapse calderas are either circular or slightly elliptical in plan view, vertical or steeply dipping, and have vertical displacements from several hundred metres to a few kilometres. 24
  • 26. ➢ SAN ANDREAS FAULT- San Andreas Fault, major fracture of the Earth’s crust in extreme western North America. The fault trends northwest for more than 800 miles (1,300 km) from the northern end of the Gulf of California through western California, U.S., passing seaward into the Pacific Ocean in the vicinity of San Francisco. Tectonic movement along the fault has been associated with occasional large earthquakes originating near the surface along its path, including a disastrous quake in San Francisco in 1906, less serious event there in 1989, and destructive quake centred in the Los Angeles suburb of Northridge in 1994 that occurred along one of the San Andreas’s larger secondary faults. • DESCRIPTION- 26
  • 27. SAN ANDREAS FAULT • HISTORY- The San Andreas Fault was born about 30 million years ago in California, when the Pacific Plate and the North America plate first met. The new configuration meant the two plates slid past one another instead of crashing into each other, a boundary called a strike-slip fault. 27
  • 28. Researchers have measured identical rocks offset by 150 miles (241 kilometers) across either side of the fault. For example, the volcanic rocks in Pinnacles National Park south of Monterey match volcanic rocks in Los Angeles County (called the Neenach volcanics). Geologists think the total amount of displacement along the fault is at least 350 miles (563 km) since it formed. • Earthquake prediction- The San Andreas Fault was the site of a massive effort to drill into Earth's crust and investigate a fault at depth. In 2004, work began near the town of Parkfield on the San Andreas Fault Observatory at Depth(SAFOD) to drill nearly 2 miles (3.2 km) into the fault. Parkfield, in central California, pops off a moderate earthquake of around magnitude 6 every couple decades, and is a center for earthquake research. Scientists predicted another earthquake should occur in 1993, but it didn't happen until 2004. Previous quakes hit in 1857, 1881, 1901, 1922, 1934 and 1966. Rocks retrieved from the deep drilling project revealed that slippery clays may be responsible for some of the "creeping" behavior along the San Andreas Fault. 28
  • 29. ➢ DIP AND STIRE- Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25°E for a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25°E would simply be 025), or the azimuth number followed by the degree sign (example of N25°E would be 025°). One technique is to always take the strike so the dip is 90° to the right of the strike, in which case the redundant letter following the dip angle is omitted (right hand rule, or RHR). STIRE AND SIP OF BED 29
  • 30. ➢ HADE AND THROW- Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation (strain) in the rocks, and ultimately, to understand the stress field that resulted in the observed strain and geometries. • HADES- Slip is defined as the relative movement of geological features present on either side of a fault plane. A fault's sense of slip is defined as the relative motion of the rock on each side of the fault with respect to the other side. In measuring the horizontal or vertical separation, the throw of the fault is the vertical component of the separation and the heave of the fault is the horizontal component, as in "Throw up and heave out". • THROW- 30
  • 31. HADE AND THROW FAULTS 31
  • 32. ➢ PARTS OF FOLDS- In a series of folds it is evident like waves. They consist of alternate crests and troughs. The crest of the fold is termed as anticline while the trough is called synclines. An anticline and syncline constitute a fold. Limbs or Flanks: Limbs or a flank of the fold is sloping side from the crest to the trough. Axial plane: An imaginary plane bisecting the vertical angle between equal slopes on either sides of the crest line. Axis of the fold: The line that divides the section of the fold. 32
  • 33. • TYPES OF FOLDS- 1. Homocline: Beds dipping in one direction but at the same angle. 2. Monocline: Infect beds, there are steep dip at one or two places. Such a bed where inclination is high at one or two places compared to the rest. Homocline 3. Structural Terrace: A bed, which is inclined in one direction, may become more or less flat at one place. 4. Anticline and Syncline- Anticline is simple fold, which is convex upwards. In Greek it means opposite inclined. In this fold the limbs dip always from each other. Syncline is simple fold, which is concave upwards. In Greek it means together inclined. In this fold the limbs dip towards each other.33
  • 34. 5. Overturned Fold: In this fold the two limbs dip in the same direction but at different angles. The axial plane is inclined. 6. Isoclinal Fold: In Greek Isoclinal fold means the two limbs dip in the same direction but at the same angle. 7. Chevron Fold: Usually the crest and troughs of a fold are rounded, but sometimes the folds are characterised by sharp crests and troughs. Such folds where the crests and troughs are sharp and angular are called Chevron Folds. 8. Recumbent Fold: A fold in which the axial plane is absolutely horizontal and the limbs are also more or less horizontal is called Recumbent Fold as in the accompanying. 9. Drag Fold: These are minor or small folds formed when competent beds (weak beds) moves over the incompetent beds. Drag fold34
  • 35. 10. Anticlinorium and Synclinorium: Anticlinorium and Synclinorium are called respectively to exceptionally large sized fold. Anticline and Syncline when it is composite fold. An Anticlinorium is a fan shaped structure and the trend if the fold is anticline character. 35