1. Radiocarbon age-modelling I – introduction to age-models
Dr. Maarten Blaauw
School of Geography, Archaeology and Palaeoecology
Queen’s University Belfast
Northern Ireland 1

2. My background Born 1974 in Hardenberg (nl)
‘92-’98 Msc Biology, Groningen (nl)
‘98-‘03 PhD Palaeoecology, Amsterdam (nl)
‘03-’04 Postdoc Trinity College Dublin (ie)
‘04-’06 Postdoc CIMAT (mx)
‘ Postdoc Queen’s Univ Belfast (uk) 2

3. Today Lectures Introduction to age-depth modelling
Bayesian age-depth modelling
Practicals
Calibrating
Basic age-depth modelling 3

4. Pollen-diagram 4
Blaauw et al. in press, The Holocene 4 4

5. Poisson random walk 5
Blaauw et al. in press, The Holocene 5 5

6. Blaauw et al. in press, The Holocene6
Blaauw et al. in press, The Holocene 6 6

7. Blaauw et al. in press, The Holocene7
Blaauw et al. in press, The Holocene 7 7

8. Types of chronologies No uncertainties Yearly resolution
Decadal / centennial – (multi-) millennial resolution 8

10. Annually layered ice cores10

11. History peat dating Pre 14C dating (relative dating)
Peat stratigraphy (Sernander ) & pollen
Link pollen with archaeology (bronze age etc.)
Link with Swedish varve chronology (de Geer)
(Sub) millennial precision
Von Post 1946 11

12. History peat dating Carbon dating → 'absolute', independent dates
Smith & Pilcher 1973: 14C dating vs. pollen zones
'Wishful thinking obscures reality' (von Post 1946)
14C date depths along peat core
At levels with major proxy changes
At regular intervals
Assume linear accumulation between dated levels
e.g.: Aaby 1976, van Geel 1978 12

13. History peat dating High-resolution 14C dating
wiggle-match dating (van Geel&Mook 1989)
Bayesian (e.g., Blaauw&Christen 2005)
post-bomb dating (e.g., van der Linden et al. 2008)
Tephra (e.g., Pilcher et al. 1995, Davies et al. 2003)
210Pb dating (e.g., Turetsky et al. 2004)
All form age estimates for age-depth models
The estimates and models are uncertain 13

14. Carbon dating 14

15. 14C dating 14C unstable, half-life 5568 yr
Ratio 14C/C gives age fossil 15

16. Belfast Seattle Tree-ring coverage for IntCal04: until 12.4 kcal BP
Irish Oak
Waikato
German Oak
Groningen
German Oak
Pretoria
German Oak
German Pine
Swiss Pine
Heidelberg
Irish Oak
German Oak
Belfast
PNW/CA
German Oak
German Pine
Seattle 16

17. Tree-ring coverage for IntCal0417

18. Tree-ring coverage for IntCal0418

19. 19

20. 20

21. Age-depth modelling So now we have dates... what's next?
Estimate ages of non-dated levels
Use available information
all dates together
environmental settings site
other comparable archives 21

22. Age-depth modelling 14C and other dates Basic age-modelling techniques
interpolation, regression, spline, ...
Bayesian approaches
chron. ordering, wiggle-match dating
Compare multiple archives
tuning, eye-balling, Bayesian 22

23. Age-depth modelling 23

24. Age-depth modelling 24

25. Uncertainty accumulation25

26. Many date$ 26

27. Few dates 27

28. 28

29. Which age-depth model?
800 cm core
9 14C dates
surface = recent 29

30. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Too much weight on
individual dates? 30

31. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
date 6 = outlier 31

32. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
470 cm = hiatus 32

33. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Linear regression
470 cm = hiatus
Too narrow error ranges? 33

34. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Linear regression
Polyn. regression
470 cm = hiatus
second degree
wide uncertainties when extrapolating! 34

35. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Linear regression
Polyn. regression
Smooth spline 35

36. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Linear regression
Polyn. regression
Smooth spline
date 6 = outlier 36

37. Which age-depth model? 800 cm core 9 14C dates surface = recent
Linear interpol.
Linear regression
Polyn. regression
Smooth spline
470 cm = hiatus 37

38. Age-depth modelling How did our sediment accumulate over time?
Constant? Varying? Pulses? Hiatuses? Site settings
Should we try to fit a curve through all dates?
Balance belief in dates and belief in model
Use stratigraphic information
How many dates do I need?
The more, the better? The more problems?
Depends on your questions
“is my sediment of glacial age?” “early 8.2 k event?” 38

39. Dating uncertainties 39

40. 14C dating 40

41. 14C dating 41

42. Uncertainties dates 5 calibrated dates surface = recent
simulate yr every date
draw age-model
linear interpolation
repeat 42

43. Uncertainties dates 5 calibrated dates surface = recent
simulate yr every date
draw age-model
polynomial regression
does not cross all dots
weighted by error sizes
repeat 43

44. Uncertainties dates 44

45. Basic age-modelling Choose which one looks nicest...
How treat point estimates? (mid/max, multimodal)‏
Why just one line?
Not much literature
Bennett 1994, Bennett and Fuller 2002, The Holocene, Telford et al. 2004, QSR
Software
Calib + Excel
clam, Blaauw in press (Quaternary Geochronology) 45

46. Today Lectures Introduction to age-depth modelling
Bayesian age-depth modelling
Practicals
Calibrating
Basic age-depth modelling 46