Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


Presentation on theme: "Magnetostratigraphy Wout Krijgsman & Cor Langereis Paleomagnetic Laboratory Fort Hoofddijk Department of Earth Sciences Utrecht University."— 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 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 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

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

11 Marine magnetic anomalies

12

13

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

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 World crustal age Marine magnetic anomalies

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 Paleogene: based on radio-isotopic ages

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

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

31

32 Sicily, 2 weeks ago

33 Sampling, 15 years ago

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

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

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

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 Precession minimum Eccentricity minimum Gibliscemi, Sicily, Italy

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

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

45 PONTIAN Acc. rate in C3r = 137cm/kyr Periodicity cycles = 22.7kyr Sand-marls cycles, Mio-Pliocene, Romania Putna river section, eastern Carpathians

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 Messinian evaporites Northern Apennines (Italy)

50 Messinian Chronology

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

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

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

54 Chronology evaporites Top of Lower Evaporites 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 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

58 Mineral dating standards: Fish Canyon Tuff

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

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 ± 0.11 Ma

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

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

63 40 Ar/ 39 Ar vs astronomical ages Age (Ma) 4.31Ma Ptolemais SR3M Ma Age (Ma) Ptolemais SLM3T Messadit Me-1 Age (Ma) 6.58 Ma Messadit Me-11 Age (Ma) 6.45 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

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

69 Carpathians foredeep Stoica et al., submittted PontianDacian

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

71 Putna Valley PONTIAN Acc. rate in C3r = 137cm/kyr Periodicity cycles = 22.7kyr

72 Eastern Carpathians Southern Carpathians

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


Download ppt "Magnetostratigraphy Wout Krijgsman & Cor Langereis Paleomagnetic Laboratory Fort Hoofddijk Department of Earth Sciences Utrecht University."

Similar presentations


Ads by Google