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Magnetostratigraphy Wout Krijgsman & Cor Langereis

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Presentation on theme: "Magnetostratigraphy Wout Krijgsman & Cor Langereis"— Presentation transcript:

1 Magnetostratigraphy Wout Krijgsman & Cor Langereis
Paleomagnetic Laboratory Fort Hoofddijk Department of Earth Sciences Utrecht University

2 Magnetostratigraphy Possibilities, pitfalls and applications
Cor Langereis, Wout Krijgsman Paleomagnetic Laboratory Fort Hoofddijk Dept. of Earth Sciences, Utrecht University Giovanni Muttoni Dept. of Earth Sciences, University of Milan Manfred Menning Geoforschungs Zentrum Potsdam, Germany

3 Magnetostratigraphy a dipole reversing at irregular times

4 Origin of reversals Mantle Liquid outer core Solid inner core
Convection time scale ~100 Myr Reversal frequency, superchrons Solid inner core Diffusion time scale 3-5 kyr Stabilises geodynamo process Kuang & Bloxham, 1997 Liquid outer core Convection time scale yr Geodynamo action: Secular variation, excursions, reversals

5 GPTS: Geomagnetic Polarity Time Scale
Lavas & K/Ar dating ? Sediments (DSDP) & biostratigraphy Barcode: may give unique solutions - but of an essentially BINARY nature - and can be distorted in the rock record Marine magnetic anomalies

6 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

7 Integrated stratigraphy
Biostratigraphy - first-order chronology Magnetostratigraphy - globally synchonous barcode Cyclostratigraphy - fine-tuning & astronomical dating

8 Geomagnetic time scales

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

10 Magneto-bio-stratigraphy
Opdyke et al., 1966 - Advent of deep-sea cores: inclination only - Biostratigraphy (faunal zones) for dating

11 Marine magnetic anomalies

12 Marine magnetic anomalies

13 Marine magnetic anomalies

14 Pitman and Heirtzler, 1966

15 Marine Magnetic Anomalies
Deep Sea Cores vs.

16 Continental drift

17 Developing the GPTS

18 Paleomagnetism DRM vs. CRM: - inclination error - delayed NRM acquisition

19 Accuracy of recording reversals
Watkins, 1968

20 Geomagnetic Polarity Time Scale (GPTS) or …
Polarity zones (subchrons) or excursions (cryptochrons) ? Geomagnetic Polarity Time Scale (GPTS) or … Geomagnetic Instability Time Scale (GITS) ‘reversal excursions’

21 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.

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

23 Marine magnetic anomalies
World crustal age

24 Triassic magnetostratigraph … beyond the sea floor record

25 Even older: magneto-stratigraphy ?

26 The times they are a-changin’
(Bob Dylan, 1964) Wout Krijgsman

27 Time: dates and rates Tools: Biostratigraphy Magnetostratigraphy
Astrochronology Isotopic dating Aims: Marine-continental Paratethys-Mediterranean Synchrony-diachrony Event stratigraphy

28 Geological Time Scale Gradstein et al. (2004) GTS2004
Neogene: based on astronomical ages Why is it so important that both methods are identical? The new GTS as published last year is based on astronomical ages for the Neogene part of the time scale and on radio-isotopic ages for e.g. the Paleogene part. The geological time scale is the framework for deciphering the history of the Earth and therefore it is crucial that astronomical and radio-isotopic dating methods produce identical results. The base of the Neogene is defined in the Lemme-Carrosio section in northern Italy. This section correlated to ODP site 926 based on detailed calcareous nannofossil correlations. ODP site 926 is astronomically tuned to La2004 and yields an age of Ma. Wilson et al. (2002), Naish et al. (2001) published Ma n=19 and Ma n=52 relative to FCT 27.84, single crystal anorthoclase for two tuffs bracketing Oligocene-Miocene boundary….Still to be explained…. Paleogene: based on radio-isotopic ages

29 Magnetostratigraphy & Cyclostratigraphy
Astronomical Tuning Climate cycles Astronomical solutions Hilgen et al., 2004

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


32 Sicily, 2 weeks ago

33 Sampling, 15 years ago Sicily, 2 weeks ago

34 Cyclostratigraphy & astronomical tuning ... ATNTS in GTS2004
Accurate definition of GSSP (Oued Akrech, Hilgen et al., 2000) Lourens et al., 2004

35 Biostratigraphy vs. Magnetostratigraphy
Problems: Taxonomy Diachrony Reworking Ages Problems: Correlation Primary signal vs. overprint Ages

36 Correlation Requires unique pattern fit Magneto age 7.6 ± 0.1 K/Ar age
6.16 ± 0.30 Garces et al., 2001

37 Ages GPTS not independent of other dating techniques

38 The times they are a-changing’
Ages change with time …

39 Astrochronology Problems: Cycle recognition Phase relation Correlation
Astronomical solution

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

41 Milankovitch cycles

42 Sapropel-marl cycles, upper Miocene, Sicily
Eccentricity minimum Precession minimum Gibliscemi, Sicily, Italy

43 Partial Unit-Stratotype of the Zanclean stage (Lower Pliocene)
Punta di Maiata, Sicily, Italy

44 Lignite-marls cycles, Mio-Pliocene, Greece
Precession minimum Ptolemais quarry, Greece

45 Sand-marls cycles, Mio-Pliocene, Romania PONTIAN
Acc. rate in C3r = 137cm/kyr Periodicity cycles = 22.7kyr Putna river section, eastern Carpathians Another aspect is the Cyclic pattern of the sedimentary rocks .Vertically bedded sandstones units, alternating with finer sediments on Putna Valley. The calculated duration of each cycle is very close to 21.7 which is very close to the average duration of the Precession Cycle.

46 Clay-carbonate cycles, Miocene, Spain
Orera section, Spain

47 Clay-carbonate cycles, Triassic, USA
Painted desert/Petrified forrest, Arizona

48 Miocene APTS Astrochronology for the Late Miocene
Sections on Crete correlated bed-to-bed to Sicily Hilgen et al. (1995)

49 Northern Apennines (Italy)
Messinian evaporites Northern Apennines (Italy)

50 Messinian Chronology

51 Messinian Salinity Crisis Evaporites synchronous
all over Mediterranean at ~5.96 Ma Krijgsman et al. 1999

52 Chronology evaporites
Cyclostratigraphy Italy: Evaporites 16 cycles (Marabini and Vai, 1988)

53 Chronology evaporites
Cyclostratigraphy Spain: Evaporites cycles (Dronkert, 1976; M.S.G.l. Fortuin et al., 2000; Sed. Geol.)

54 Chronology evaporites Top of Lower Evaporites 5.60-5.52 Ma
(Krijgsman et al. 2001; Sed. Geol.)

55 La93 <> La2004

56 Radio-Isotopic dating
Problems: Technique (K/Ar vs. Ar/Ar) Error determination Mineral dating standards

57 Error determination Ar/Ar ratio: mass spectrometer precision depends on e.g. measurement protocol, mass discrimination Decay constant J is an irradiation parameter and its accuracy depends on an accurately known age of a mineral standard.

58 Mineral dating standards:
Fish Canyon Tuff

59 Magnetostratigraphy Tortonian Salinity Crisis: Fortuna Basin
Betic Corridor problem K/Ar age of 6.16 ± 0.30 Ar/Ar age of 7.71 ± 0.11 Magnetostratigraphy Tortonian Salinity Crisis: Fortuna Basin (Garces et al. 1998; 2001)

60 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 ± Ma

61 Isotopic ages and astronomical ages
Intercalibration Isotopic ages and astronomical ages Faneromeni section: Messinian, Crete

62 40Ar/39Ar vs. astronomical ages
6.94 Ma Fan-a1, Crete Miocene, marine 2: 0.01 Ma; N = 44 3 different irradiations 6.65 6.75 6.85 6.95 7.05 7.15 Age (Ma) Kuiper et al., 2003

63 40Ar/39Ar vs astronomical ages
Ptolemais SR3M Ptolemais SLM3T 4.31Ma 4.39 Ma 4 4.1 4.2 4.3 4.4 4.5 4 4.1 4.2 4.3 4.4 4.5 Age (Ma) Age (Ma) Messadit Me-11 Messadit Me-1 6.45 Ma 6.58 Ma 6.2 6.3 6.4 6.5 6.6 6.7 6.2 6.3 6.4 6.5 6.6 6.7 Age (Ma) Age (Ma)

64 Intercalibration Isotopic ages and astronomical ages Morocco / Spain
Kuiper et al., 2008

65 Intercalibration Inter-laboratory calibration
Kuiper et al., 2008 (Science)

66 Intercalibration Isotopic ages and astronomical ages
K/T Boundary Zumaia (Spain): new age of Ma

67 Mediterranean vs Paratethys
Late Miocene -Early Pliocene Since the end of Oligocene, Paratethys area evolved as the northern branch of the Neo- Tethys Ocean while its southern branch is the actual Mediterranean region. It is very important to know the connections between water masses. When they were open or closed we do not know. We do not know even all of them were there or not. Taking into account that we that for Mediterranean already exists a very good time frame we want to do the same for the eastern Paratethys. EVOLVED

68 ‘Evolution’ of the Time Scales from Eastern Paratethys
~3Ma ~0.3Ma 10 TIMES longer

69 Carpathians foredeep Pontian Dacian Stoica et al., submittted

70 Carpathians foredeep EC SC Vasiliev et al., 2004; 2005

71 Putna Valley PONTIAN Acc. rate in C3r = 137cm/kyr
Periodicity cycles = 22.7kyr Another aspect is the Cyclic pattern of the sedimentary rocks .Vertically bedded sandstones units, alternating with finer sediments on Putna Valley. The calculated duration of each cycle is very close to 21.7 which is very close to the average duration of the Precession Cycle.

72 Eastern Southern Carpathians Carpathians
Schematic time scale for Mediterranean. The local stage boundaries show no direct connection with the changing from Mediterranean. The desiccation and the Pliocene flooding from Mediterranean seems to not be reflected at all in the western most part of the eastern Paratethys. Anyway the presumed influx of Paratethyan water into Mediterranean did not left any sign in Paratethys. no clue. The Meotian/Pontian boundary which was associated previously with the Tortonian/Messinian boundary can be maybe connected now with the onset of the Messinian Salinity crisis. The change in the magnetic components from oxic to anoxic conditions reveal a huge change in the basin configuration occurring at the Me/Po boundary, in the C3r chron. It may be related to the MsC or not. Eastern Carpathians Southern Carpathians

73 The evolution of Paratethys: the lost sea of Central Eurasia
Vici project 2011 3 PhD / 2 Postdoc positions

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