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The Rock Record: Determining Relative Age Chapter 8

The Rock Record: Determining Relative Age Chapter 8. Rocks Tell a Story!!!. How do we know what happened?. Relative Dating – tells which one is older, not actual age Absolute Dating – actual age. Determining Relative Age. James Hutton discovered that the present is the key to the past.

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The Rock Record: Determining Relative Age Chapter 8

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  1. The Rock Record: Determining Relative Age Chapter 8

  2. Rocks Tell a Story!!!

  3. How do we know what happened? Relative Dating – tells which one is older, not actual age Absolute Dating – actual age

  4. Determining Relative Age • James Hutton discovered that the present is the key to the past. • Principle of Uniformitarianism:

  5. Layers of rock called strata tell the story of what came first. • A relative age (older vs. younger) can be determined with a few simple laws.

  6. Law of Original Horizontality • Sedimentary rocks left undisturbed will remain in horizontal layers.

  7. Law of Inclusions • Rock fragments (in another rock) must be older than the rock containing the fragments.

  8. ...sandstone is older. ...granite is older.

  9. Law of Crosscutting Relationships A fault or an intrusion is always younger than the rock layers it cuts through.

  10. UNCONFORMITIES Gaps in the geologic record when deposition stopped, rock was eroded away, and then deposition restarted. There are 3 types: 1. Angular Unconformity 2. Disconformity 3. Nonconformity

  11. Angular Unconformity • Boundary between a tilted layer and a horizontal layer

  12. Disconformity • Nearly horizontal Boundary between layers of rock that have not been deposited continuously • A large time gap exists.

  13. Nonconformity • Boundary where stratified (layered) rock rests on unstratified rock

  14. Possible Solution1. Deposition of shale2. Deposition of conglomerate3. Deposition of sandstone4. Deposition of lithic sandstone5. Deposition of limestone6. Deposition of quartz sandstone7. Deposition of limey shale8. Deposition of mudstone9. Intrusion of granite. This may have occurred earlier. However, as granites are emplaced at depth, it is assumed all the sequence was deposited and lithofied prior to emplacement.10. Uplift and erosion to form current land surface.11. Deposition of alluvium

  15. Possible Solution1. Deposition of conglomerate2. Deposition of sandstone3. Deposition of limestone4. Deposition of shale5. Deposition of mudstone6. Faulting7. Intrusion of gabbro

  16. Possible Solution1. Deposition of Quarry Shale2. Deposition of Cave Bluff Limestone3. Deposition of Redin Sandstone4. Deposition of Tinely Ashstone5. Deposition of Clipton Volcanics6. Folding7. Intrusion of basalt dyke8. Faulting

  17. Possible Solution1. Deposition of Davin Shale2. Deposition of Hutt Ashstone3. Deposition of Cabin Limestone4. Deposition of Lower Coal Seam5. Deposition of Ravin Sandstone6. Deposition of Blackman Shale7. Deposition of Fossil Bed Limestone8. Folding9. Uplift and erosion (forming unconformity surface)10. Deposition of Basin Conglomerate11. Deposition of Log Creek Mudstone12. Deposition of Loren Shale13. Deposition of Jackson Sandstone14. Intrusion of basalt dyke15. Tilting16. Erosion to form present landscape.

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