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Relative age – The principle of uniformitarianism

Relative age – The principle of uniformitarianism. (The present is the key to the past). Recent mudcracks. Paleozoic mudcracks. (245 to 570 million years). Relative age – The principle of superposition. Relative age – The principle of original horizontality.

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Relative age – The principle of uniformitarianism

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  1. Relative age – The principle of uniformitarianism (The present is the key to the past) Recent mudcracks Paleozoic mudcracks (245 to 570 million years)

  2. Relative age – The principle of superposition

  3. Relative age – The principle of original horizontality

  4. Relative Age – The Principle of Original Continuity

  5. Relative age – Crosscutting relationships

  6. Relative age – Cross-cutting relationships

  7. Relative age and the fossil record Bryozoan Crinoid Brachiopod

  8. Relative age – index fossils fossil assemblages, and global correlation

  9. Unconformities and gaps in time Non-conformity Angular unconformity

  10. Sandstone 375 Ma Limestone 450 Ma Angular Unconformity

  11. Disconformity

  12. Developing a Geological Map

  13. Stratigraphic succession at the Grand Canyon

  14. Grand Canyon Stratigraphy

  15. Stratigraphic correlation

  16. Stratigraphic Correlation Cross-section 3 Cross-section 2 Cross-section 1

  17. Cross-section 1 Cross-section 2 Cross-section 3

  18. Global Stratigraphic Correlation The role of fossil assemblages

  19. Radioactive Isotope Decay Alpha decay Beta - minus decay

  20. Radiometric Age Dating Parent Radioactive decay Half-life Daughter 4.47x109 yr 206Pb 238U N =Noe -lt (N = number of parent atoms at time t; No = initial number of parent atoms; l = rate constant or proportion of atoms destroyed per year) 235U 207Pb 704x106 yr Half-life 40Ar 40K 1.25x109 yr ½ = e-lt/2 14C 5,730 yr 14N

  21. 14 14 n + N C + p 7 6 _ _ 14 14 6 7 Radiocarbon (14C) Dating Neutrons produced from cosmic radiation undergo nuclear reactions with nitrogen in the atmosphere to produce carbon 14. Plants take up carbon 14 by absorbing CO2 After death the proportion of carbon 14 slowly decreases due to beta-minus decay _ β C N + v + e

  22. Geological Time Scale Proliferation of shelly fossils

  23. Geological Time

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