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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.

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Presentation on theme: "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."— Presentation transcript:

1 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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3 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.

4 Unconformity 1.Deposition of sandstone

5 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale

6 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone

7 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone

8 Principle of original horizontality Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level

9 Principle of erosional unconformities Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.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.

10 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone

11 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale

12 Principle of cross-cutting relationships Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite

13 Principle of cross-cutting relationships Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite 11.Faulting

14 Principle of erosional unconformities Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite 11.Faulting 12.Uplift and/or falling sea level 13.Erosion forming a disconformity

15 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite 11.Faulting 12.Uplift and/or falling sea level 13.Erosion forming a disconformity 14.Subsidence and/or rising sea level 15.Deposition of limestone

16 Principle of superposition Unconformity 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite 11.Faulting 12.Uplift and/or falling sea level 13.Erosion forming a disconformity 14.Subsidence and/or rising sea level 15.Deposition of limestone 16.Deposition of shale

17 Modern land surface 1.Deposition of sandstone 2.Deposition of shale 3.Deposition of limestone 4.Deposition of sandstone 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity 7.Subsidence and/or sea level rise 8.Deposition of sandstone 9.Deposition of shale 10.Intrusion of granite 11.Faulting 12.Uplift and/or falling sea level 13.Erosion forming a disconformity 14.Subsidence and/or rising sea level 15.Deposition of limestone 16.Deposition of shale 17.Uplift and/or falling sea level 18.Formation of the modern land surface

18 1.Deposition of sandstone H 2.Deposition of shale C 3.Deposition of limestone J 4.Deposition of sandstone I 5.Tilting and uplift and/or falling sea level 6.Erosion forming an angular unconformity G 7.Subsidence and/or sea level rise 8.Deposition of sandstone K 9.Deposition of shale L 10.Intrusion of granite E 11.Faulting D 12.Uplift and/or falling sea level 13.Erosion forming a disconformity B 14.Subsidence and/or rising sea level 15.Deposition of limestone A 16.Deposition of shale F 17.Uplift and/or falling sea level 18.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


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