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Understanding Earth's History: Fossils and Dating Methods

Explore the fossil record, geologic time, relative and absolute dating principles in geology. Learn to sequence events, uncover past environments, and decipher the Earth's history. Engage in labs and activities to enhance understanding of geologic concepts.

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Understanding Earth's History: Fossils and Dating Methods

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  1. Geology 12 Presents

  2. Hand out note helper WS 8.45

  3. Unit Outline • A: Fossil Record & Geologic Time • WSs: 8.1, 8.2, 8.3, & 8.4 • Labs: 8.1, 8.2 & 8.3 (bonus) • B: Relative Dating • WS: 8.5, Lab 8.4 • C: Absolute Dating • WS 8.5, Lab 8.5 • Unit 2 Review WS + Unit 2 Test

  4. B: Relative Dating • Order of events: write numbers on sheet. 8 7 6 5 = erosion 4 = tilting 9 3 2 1

  5. Relative Dating

  6. Relative Dating • Involves placing events in the correct sequence or order 15 = erosion 14 13 12 = erosion 10 9 8 = erosion 11 =faulting 7 = tilt = mtn’ bldg’ 5 3 4 6 2 1

  7. Absolute Dating is determining how long ago something happened (ma) • ie. Dinosaurs became extinct 65 ma ago. • Using the principle of Uniformitarianism, six principles have been developed

  8. 1. Principle of Superposition: oldest rocks on bottom; youngest rocks on top.

  9. 2. Principle of Original Horizontality: sediments deposited in water in horizontal manner.

  10. 3. Principle of Lateral Continuity: sediments continue in all directions until they thin and are pinched out at the edge of the basin.

  11. 4. Principle of Cross-cutting Relationships: an igneous intrusion (or fault) is younger than the rock it intrudes (crosses). 4 3 2 1

  12. 6 5 7 4 3 8 9 2 1

  13. 17-erosion 6 5 12 8-erosion 11 10 9 14 4 3 7 2 15 1 16 13

  14. 5. Principle of Inclusions: xenoliths/ inclusions are older than the rocks they’re in. 2 1 3

  15. 2 1 3

  16. 4 3 3 2 5 - erosion 2 5 - erosion 1 1 4

  17. 7 6 5 4 3 2 1

  18. 6. Principle of Fossil Succession: fossils on bottom are older than fossils on top.

  19. Unconformities • Break or portion of time (hiatus) is missing • Cause: period of non-deposition, period of erosion or mountain building • 3 types

  20. 1. Disconformity: surface of erosion or non-deposition (hard to detect) weathering, oxidation, jointing, etc. Sed’ Rx Sed’ Rx

  21. 2. Angular Unconformity: beds tilted then eroded before deposition (most common on exam)

  22. Angular Unconformity

  23. 3. Nonconformity: erosion surface is cut into metamorphic or igneous rocks. Use principle of inclusions to determine if it is an intrusion or a nonconformity. Sed’ Rx Ign’ or met’ Rx

  24. Practice Relative Dating Examples

  25. Do Lab 8-4 Relative Dating • Work on WS 8-5 • Work on Chp. 8 Review WS

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