Magnetostratigraphy

Wout Krijgsman & Cor Langereis

Paleomagnetic Laboratory

Fort Hoofddijk

Department of Earth Sciences

Utrecht University

MagnetostratigraphyPossibilities, pitfalls and applications

Cor Langereis, Wout KrijgsmanPaleomagnetic Laboratory Fort Hoofddijk

Dept. of Earth Sciences, Utrecht

University

Giovanni MuttoniDept. of Earth Sciences, University of

Milan

Manfred MenningGeoforschungs Zentrum Potsdam,

Germany

Magnetostratigraphya dipole reversing at irregular times

Origin of reversals

MantleConvection time scale ~100 MyrReversal frequency, superchrons

Solid inner coreDiffusion time scale 3-5 kyrStabilises geodynamo process

Kuang & Bloxham, 1997

Liquid outer coreConvection time scale 300-500 yrGeodynamo action: Secular variation, excursions, reversals

Barcode: may give unique solutions- but of an essentially BINARY nature- and can be distorted in the rock record

Sediments (DSDP) & biostratigraphy

Marine magnetic anomalies

Lavas & K/Ar dating

?

GPTS: Geomagnetic Polarity Time Scale

Magnetostratigraphy part of integrated stratigraphy

Biostratigraphy: first-order chronology

- taxonomy, reworking, diachrony, ages

Magnetostratigraphy: globally synchonous

barcode

- depends on good paleomagnetic signal &

recording

Cyclostratigraphy: astronomical dating, fine-

tuning

- astronomical solutions (> 20 Ma)

- interpretation of phase relations

Integrated stratigraphy

Biostratigraphy

- first-order chronology

Magnetostratigraphy

- globally synchonous barcode

Cyclostratigraphy

- fine-tuning & astronomical dating

Geomagnetic time scales

K/Ar dating of lavas Cox et al., 1964

Magneto-bio-stratigraphy

Opdyke et al., 1966

- Advent of deep-sea cores: inclination only- Biostratigraphy (faunal zones) for dating

Marine magnetic anomalies

Marine magnetic anomalies

Marine magnetic anomalies

Pit

man a

nd H

eir

tzle

r,

19

66

MarineMagneticAnomalies

DeepSeaCores

vs.

Continental drift

Developing the GPTS

Paleomagnetism

DRM vs. CRM:

- inclination error

- delayed NRM acquisition

Accuracy of recording reversals

Watkins, 1968

Geomagnetic Polarity Time Scale(GPTS)

or …

Geomagnetic Instability Time Scale(GITS)

‘reversal excursions’

Polarity zones (subchrons) or excursions (cryptochrons) ?

Magnetostratigraphic resolution

Laj & Channell (2007) proposed:

Resolution depends on:- sampling resolution (easy … just take more samples)- sediments: sedimentation rate & suitable recording medium- diagenesis, lock-in depth, overprints, etc., etc.

Magnetostratigraphic resolution

Nomenclature OK …but for practical (integrated) stratigraphy and constraints on chronostratigraphy ?

World crustal age

Marine magnetic anomalies

Triassic magnetostratigraph… beyond the sea floor record

Even older:

magneto-stratigraphy ?

The times they are a-changin’

(Bob Dylan, 1964)

Wout Krijgsman

Time: dates and rates

Tools:BiostratigraphyMagnetostratigraphyAstrochronologyIsotopic dating

Aims:Marine-continentalParatethys-MediterraneanSynchrony-diachronyEvent stratigraphy

Geological Time Scale

Gradstein et al. (2004)

GTS2004

Neogene:based on astronomical ages

Paleogene:based on radio-isotopic ages

Hilgen et al., 2004

Magnetostratigraphy & Cyclostratigraphy

Astronomical Tuning

Climate cycles

Astronomical solutions

Astronomical Polarity Time Scale (APTS) Astronomical Polarity Time Scale (APTS) for the Mediterranean Neogenefor the Mediterranean Neogene

Sicily, 2 weeks ago

Sicily, 2 weeks ago

Sampling, 15 years ago

Lourens et al., 2004

Cyclostratigraphy & astronomical tuning ... ATNTS in GTS2004

Accurate definition of GSSP (Oued Akrech, Hilgen et al., 2000)

Biostratigraphy vs. Magnetostratigraphy

Problems:• Taxonomy• Diachrony• Reworking• Ages

Problems:• Correlation• Primary signal

vs. overprint• Ages

Correlation

Requires

unique pattern fit

Garces et al., 2001

K/Ar age6.16 ± 0.30

Magneto age7.6 ± 0.1

Ages

GPTS not independent of other dating techniques

The times they are a-changing’

Ages change with time …

Astrochronology

Problems:• Cycle recognition• Phase relation• Correlation• Astronomical solution

Astrochronology: correlation of cyclic variations in the geological record to computed astronomical (age) curves

Eccentricity from -1200 kyr to -0 kyr (La90)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 200 400 600 800 1000 1200

Age (in kyr)

ecce

ntric

ity

Obliquity from -1200 kyr to -0 kyr (La90)

21.5

22

22.5

23

23.5

24

24.5

25

0 200 400 600 800 1000 1200

Age (in kyr)

ob

liqu

ity

Precession - Eccentricity -1200 to 0 kyr (La90)

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0 200 400 600 800 1000 1200

Age (in kyr)

prec

essi

on /

ecc

entr

icity

Milankovitch cycles

Sapropel-marl cycles, upper Miocene, Sicily

Precessionminimum

Eccentricityminimum

Gibliscemi, Sicily, Italy

Partial Unit-Stratotype of the Zanclean stage (Lower Pliocene)

Punta di Maiata, Sicily, Italy

Precessionminimum

Lignite-marls cycles, Mio-Pliocene, Greece

Ptolemais quarry, Greece

PONTIANAcc. rate in C3r = 137cm/kyrPeriodicity cycles = 22.7kyr

Sand-marls cycles, Mio-Pliocene, Romania

Putna river section,eastern Carpathians

Clay-carbonate cycles, Miocene, Spain

Orera section, Spain

Clay-carbonate cycles, Triassic, USA

Painted desert/Petrified forrest, Arizona

MioceneAPTS

• Astrochronology for

the Late Miocene

• Sections on Crete

correlated bed-to-

bed to Sicily

Hilgen et al. (1995)

Messinian evaporitesNorthern Apennines (Italy)

Messinian Chronology

Messinian Salinity Crisis

Krijgsman et al. 1999

Evaporites synchronousall over Mediterraneanat ~5.96 Ma

La93 <> La2004

Radio-Isotopic dating

Problems:• Technique (K/Ar vs. Ar/Ar) • Error determination• Mineral dating standards

]Ar[

]Ar[J1ln

λ

1t

39

*40

K

Ar/Ar ratio: mass spectrometer precision depends on e.g. measurement protocol, mass discrimination

J is an irradiation parameter and its accuracy depends on

an accurately known age of a mineral standard.

Decay constant

Error determination

Mineral dating standards:

Fish Canyon Tuff

Betic Corridor problem

Magnetostratigraphy Tortonian Salinity Crisis: Fortuna Basin

(Garces et al. 1998; 2001)

K/Ar age of6.16 ± 0.30

Ar/Ar age of7.71 ± 0.11

Method

Garces et al. (2001) Magnetic age: 7.6 ± 0.1 Ma

Bellon et al. (1983) K/Ar age: 6.16 ± 0.30 Ma

Kuiper et al. (2002) Ar/Ar age: 7.71 ± 0.11 Ma

40Ar/39Ar vs. astronomical ages

Fan-a1, CreteMiocene, marine

2: 0.01 Ma; N = 443 different irradiations

6.65 6.75 6.85 6.95 7.05 7.15

Age (Ma)

6.94 Ma

Kuiper et al., 2003

Intercalibration

Isotopic ages and astronomical ages

Morocco / Spain

Kuiper et al., 2008

Intercalibration

Inter-laboratory calibration

Kuiper et al., 2008 (Science)

Intercalibration

Isotopic ages and astronomical ages

K/T Boundary Zumaia (Spain): new age of 65.96 Ma

Mediterranean vs ParatethysLate Miocene -Early Pliocene

‘Evolution’ of the Time Scales from Eastern Paratethys

10 TIMES longer~3Ma

~0.3Ma

Carpathians foredeep

Stoica et al., submittted

Pontian Dacian

Carpathians foredeep

SC

EC

Vasiliev et al., 2004; 2005

Putna Valley PONTIANAcc. rate in C3r = 137cm/kyrPeriodicity cycles = 22.7kyr

EasternCarpathians

SouthernCarpathians

The evolution of Paratethys: The evolution of Paratethys:

the lost sea of Central Eurasiathe lost sea of Central Eurasia

Vici project 2011Vici project 2011

3 PhD / 2 Postdoc positions3 PhD / 2 Postdoc positions