Assignment #3 The relative age of rocks and geological events.
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Assignment #3 The relative age of rocks and geological events. The uppermost surface is the modern land surface which is slowly undergoing erosion in response to processes at the earth’s surface. The figure on the right is a geological cross-section showing the distribution of rocks, faults and unconformities. Unconformity Modern land surface The geology shown in the cross-section is due to changing environmental conditions (related to rising and falling sea level and/or subsidence and uplift of the land surface) along with igneous intrusion and faulting. The sequence of events that led to the distribution shown can be determined using the basic principles covered in the lecture on relative time.
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Assignment #3 The relative age of rocks and geological events. Unconformity. The figure on the right is a geological cross-section showing the distribution of rocks, faults and unconformities. Modern land surface. - PowerPoint PPT Presentation
Transcript of Assignment #3 The relative age of rocks and geological events.
Assignment #3The relative age of rocks and
geological events.
The uppermost surface is the modern land surface which is slowly undergoing erosion in response to processes at the earth’s surface.
The figure on the right is a geological cross-section showing the distribution of rocks, faults and unconformities.
Unconformity
Modern land surface
The geology shown in the cross-section is due to changing environmental conditions (related to rising and falling sea level and/or subsidence and uplift of the land surface) along with igneous intrusion and faulting.
The sequence of events that led to the distribution shown can be determined using the basic principles covered in the lecture on relative time.
Principle of Erosional unconformities: unconformities are younger than the rocks that they affect.
The following slides illustrate the sequence of events that would produce the geology shown in the geological cross-section on the first slide. They also tell you which of the principles is used to determine the relative order of events.
Unconformity
1. Deposition of sandstone
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone
Principle of original horizontality
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level
Principle of erosional unconformities
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity
Assignment hint: Note that unconformities that are tilted, but parallel to underlying strata, formed prior to the event that caused the tilting.
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale
Principle of cross-cutting relationships
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite
Principle of cross-cutting relationships
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite11. Faulting
Principle of erosional unconformities
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite11. Faulting12. Uplift and/or falling sea level13. Erosion forming a disconformity
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite11. Faulting12. Uplift and/or falling sea level13. Erosion forming a disconformity14. Subsidence and/or rising sea level15. Deposition of limestone
Principle of superposition
Unconformity
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite11. Faulting12. Uplift and/or falling sea level13. Erosion forming a disconformity14. Subsidence and/or rising sea level15. Deposition of limestone16. Deposition of shale
Modern land surface
1. Deposition of sandstone2. Deposition of shale3. Deposition of limestone4. Deposition of sandstone5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity7. Subsidence and/or sea level rise8. Deposition of sandstone9. Deposition of shale10. Intrusion of granite11. Faulting12. Uplift and/or falling sea level13. Erosion forming a disconformity14. Subsidence and/or rising sea level15. Deposition of limestone16. Deposition of shale17. Uplift and/or falling sea level18. Formation of the modern land surface
1. Deposition of sandstone H2. Deposition of shale C3. Deposition of limestone J4. Deposition of sandstone I5. Tilting and uplift and/or falling sea level6. Erosion forming an angular unconformity G7. Subsidence and/or sea level rise8. Deposition of sandstone K9. Deposition of shale L10. Intrusion of granite E11. Faulting D12. Uplift and/or falling sea level13. Erosion forming a disconformity B14. Subsidence and/or rising sea level15. Deposition of limestone A16. Deposition of shale F17. Uplift and/or falling sea level18. Formation of the modern land surface
Unconformity
Modern land surface
A
I
C
D
E
G
H
F
B
J
K L
In the assignment each lithological unit, fault, intrusion and unconformity is labeled with a letter. In your sequence of events you must include the letter associated with each as shown in the example above.
Note that even though units H, C, I, J, K and L are not laterally continuous due to faulting, the Principle of lateral continuity allows you to recognize that they are the same units in the same sequence on either side of the fault.
Youngest
Oldest
