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Magnetostratigraphy

Magnetostratigraphy. Wout Krijgsman & Cor Langereis Paleomagnetic Laboratory Fort Hoofddijk Department of Earth Sciences Utrecht University. Magnetostratigraphy Possibilities, pitfalls and applications. Cor Langereis, Wout Krijgsman Paleomagnetic Laboratory Fort Hoofddijk

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Magnetostratigraphy

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

  2. MagnetostratigraphyPossibilities, 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. Magnetostratigraphya dipole reversing at irregular times

  4. Mantle Convection time scale ~100 Myr Reversal frequency, superchrons Liquid outer core Convection time scale 300-500 yr Geodynamo action: Secular variation, excursions, reversals Solid inner core Diffusion time scale 3-5 kyr Stabilises geodynamo process Kuang & Bloxham, 1997 Origin of reversals

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

  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. MarineMagneticAnomalies DeepSeaCores vs.

  16. Continental drift

  17. Developing the GPTS

  18. PaleomagnetismDRM 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 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 ScaleGradstein et al. (2004)GTS2004 Neogene: based on astronomical ages Paleogene: based on radio-isotopic ages

  29. Magnetostratigraphy & Cyclostratigraphy Astronomical TuningClimate cyclesAstronomical solutions Hilgen et al., 2004

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

  31. Sicily, 2 weeks ago

  32. Sampling, 15 years ago Sicily, 2 weeks ago

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

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

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

  36. Ages GPTS not independent of other dating techniques

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

  38. Astrochronology • Problems: • Cycle recognition • Phase relation • Correlation • Astronomical solution

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

  40. Milankovitch cycles

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

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

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

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

  45. Clay-carbonate cycles, Miocene, Spain Orera section, Spain

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

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

  48. Messinian evaporites Northern Apennines (Italy)

  49. Messinian Chronology

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