SUPRA-net:Chronological information and uncertainty

Radiocarbon dating & calibration - Paula Reimer

Age-depth modeling – Maarten Blaauw

Optical stimulated luminescence – Mark Bateman

Tephrochronology – David Lowe

U series dating – David Richards*

Combining multiple dating techniques – Andrew Millard

Ice Cores: Overview of dating methods - Regine Röthlisberger

Stratigraphical constraints on marine reservoir corrections –Luke Skinner

Modeling marine reservoir corrections – Gerrit Lohmann

Common sources of chronological uncertainties•Sampling interval

•Material dated vs. time of event or proxy change

•Transfer of timescale to companion cores

•Hiatuses and other sedimentary processes

•Bioturbation

Austin et al. 1995

https://cams.llnl.gov/

Radiocarbon dating & calibration uncertainties

•Sampling

Measurement

•Age calculation

•Contamination

•Calibration

•Marine reservoircorrections

S7 2QW,

Radiometric dating (no daugher decay)

S7 2QW,

Measurement uncertainties

Animation: M. Blaauw

Poisson nature of radioactivedecay and AMS counts

Animation: M.Blaauw

Vogel et al. 2004

Age calculation uncertainties

Libby half-life

5568 ± 30 years – canceled in calibration

Isotope fractionation correction: 13C uncertainty

• Estimated ± 1 - 2 ‰ (± 8-32 years)• Measured off-line ± 0.2 ‰ (± 2)- ok in gas counting systems- may not be equivalent to fractionation in AMS machine)• Measured in AMS ± 1 ‰ (± 16 years)

Age calculation and uncertainties

Measurement uncertainties

TIRI 1993 (Scott et al. 2003)

Estimating laboratory precision through replicates

14C age BP

Num

ber

ofsa

mpl

esDendrodated wood

scatter/ meas = 1.17

(lab error multiplier)

14C calibration uncertainties

Animation: M. Blaauw

Constant initial 14C

IntCal04Calibration curve

IntCal04 Radiocarbon calibration

Tree-ring 14C

Proposed IntCal extension 2008

Fairbanks corals

Bard corals

Iberian forams

Cariaco forams

Cutler corals

Atmospheric nuclear testing 14C

Courtesy Stewart Fallon

marine reservoir correction uncertaintiesPresent – limited pre-bomb measurements Past variations – N. Atlantic example

R values

Cape of Good Hope 224± 51

Natal 213 ± 57

St. Helena 325 ± 18Bondevik et al. 2006

Age-depth modeling – Maarten Blaauw

Uncertainty accumulation

Which age-depth model?

800 cm core

9 14C dates

surface = recent

Linear interpol.

Too much weight onindividual dates?

Which age-depth model?

800 cm core

9 14C dates

surface = recent

Linear interpol.

Linear regression

Polyn. regression

Smooth spline 470 cm = hiatus

Stratigraphic order dates

Christen, 1994. Appl Stat 43:489-503

Only accept iterations with correct order

Reduces error ranges

Removes outliers

Hard to question

Easy in Bcal / OxCal

Wiggle-match dating

Assume linear accumulation (Bpeat)‏

age = a*depth + b

Include additional information

prior outlierprobabilities

prior outlierprobabilities

other dates:tephra, pollen,210Pb, U/Th, ...

hiatus, size

Grey-scale ghost graphs

Comparing multiple archives

Wunsch 2006Neff et al 2001

Comparing multiple archives

Luminescence Dating – Mark Bateman

‘I also brought it [a diamond] to somekind of glimmering light by taking intobed with me, and holding it a goodwhile upon a warm part of my nakedbody’.

Robert Boyle 1663

Includes – Thermoluminescence (TL), Optically stimulated luminescence (OSL),infrared stimulated luminescence (IRSL), Green light stimulated luminescence(GLSL) and blue light stimulated luminescence (BLSL)

TephrochronologyTephrochronology

David J. Lowe

Photo: M. Gehrels

Age estimates

“all ages are model ages”…

Growth models

“…even more so for interpolated ages”

U-Series Dating – David Richards

Multiple dating methods – a problemAndrew Millard

How to combine 14C and 210Pb dates?

Current ‘obvious’ approach is: Calculate 210Pb dates based on a sediment accumulation

model combine with 14C dates to give new accumulation model which may not be consistent with the initial accumulation

model!

Uncertainties are not properly quantified

One event

chronometricdata

date

other parameterse.g. half-life

repeat for multiplemethods

Multiple events

chronometricdata 1

date 1

other parametersmethod 1

chronometricdata 2

date 2

processmodel

Multiple events

chronometricdata 1

date 1

other parametersmethod 1

chronometricdata 2

date 2

processmodel

chronometricdata 3

date 3

other parametersmethod 2

U-series at theBourgeoisDelaunay

Bed 6

LC11 LC12

LC31LC1 & LC2

Beds 8-10

on Bed 7

Bed 7

LC2-1LC47C3 LC14D

LC47C2

LC47C1

LC2-1

LC2-1

LC14C

LC14B

LC14A

Bed 11

40 60 80 100 120 140 160 180 200 220 240 260

79 LC11-1 top

79 LC11-3 top

79 LC12-1 base

77 LC1-1

77 LC1-2

81 LC31-2

81LC31-3

81 LC47C-3

81 LC47C-2

81 LC47C-1

77 LC2-1

77 LC2-2

77 LC2-4

79 LC14D

79 LC14C-2

79 LC14B

79 LC14A-1

79 LC14A-2

Sam

ple

refe

renc

e

Date (ka)

Bed

11O

nB

ed7

Bed

7

Combining 14C and 210Pb

210Pb data date 1

sedimentaccumulation

model

14C data date 2

210Pb data date 3

14C data date 4

210Pb parameters

14C parameters

Ice Cores: Overview of dating methods - RegineRöthlisberger