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Radiometric dating / Sediment accumulation I Principles II Assumptions III 14 C Production rate Reservoir corrections Circulation effect Deep-water age.

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Presentation on theme: "Radiometric dating / Sediment accumulation I Principles II Assumptions III 14 C Production rate Reservoir corrections Circulation effect Deep-water age."— Presentation transcript:

1 Radiometric dating / Sediment accumulation I Principles II Assumptions III 14 C Production rate Reservoir corrections Circulation effect Deep-water age IV 230 Th U Decay vs. production Constant accumulation model Constant 230 Th flux model 230 Th V Other… Radiometric (Ar-Ar) Annual (varves) Cyclical (orbital)

2 Dating sediment goal Establish age-depth relationship

3 Terminology Parent Daughter Isotopes Stable Radioactive alpha, beta, gamma decay

4 Radioactive decay Spontaneous emission Nuclear transformation Loss of parent Growth of daughter

5 Definitions Decay constant Activity Half life Mean life

6 Application Balance of Resolution vs. longevity 14 C useful for last climate cycle.

7 Reporting convention Time zero = 1950 Half life = 5730 y del notation vs. stand.

8 Definitions Decay constant Activity Half life Mean life

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10 Age and accumulation Assumptions Uncertainty

11 Dating sediment goal Establish age-depth relationship

12 Bioturbation Sediment imperfect recorder Bioturbation example of filter

13 Reservoir effect Transfer from one reservoir to another takes time.

14 Variable pathways Sources Sinks

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16 Different scales Radiocarbon and calendar

17 Solar variabiluty Sunspot cycles and 14 C production

18 Age offsets Long-term trend

19 Age offsets Ocean and climate Influences possible.

20 Hughen et al. Comparisons Independent chronologies allow test of influences.

21 Age offsets

22 Evolving production Atmospheric 14 C and magnetic field inverse.

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24 14 C through time Complications of Carbon cycle, physical and chemical cycling.

25 Ocean circulation Influence on apparent age

26 Age plateaus

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28 Age anomalies Modeling ocean and production variations.

29 Uranium series Absolute chronology?

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31 Parent decay to stable daughter

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33 Secular equilibrium Between long half- life parent and shorter half-live daughter

34 Uranium series Different approaches 1.Corals 2.Deep-sea sediments

35 Uranium series Downcore approach

36 Uranium series Assume constant deposition, estimate rate.

37 Uranium series Second approach. Assume constant flux of decay product, estimate instantaneous rates of sedimentation.

38 Uranium series Reasonable assumption

39 Uranium series Integrated approach (Sacketts method).

40 Uranium series Test of (Sacketts method).

41 Uranium series Test of Sacketts method.

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43 Uranium series Works for special case.

44 Extraterrestrial IDPs New 3He approach.

45 Ar - Ar method Dating tool for longer time, lower resolution.


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