Magnetostratigraphy

Stratigraphy, from the Latin stratum (= layer) and the Greek graphere (= to describe) Literally means the description and study of - the succession of - layered rocks Stratigraphy is the science of rock strata Stratigraphy

Leonardo da Vinci ( ) fossils are not “jollies of Nature” but are remnants of once-living creatures are not the result of the deluge possibility of mountain uplift

Nicolaus Steno ( ) Niels Stensen Laws of Steno (1669) Modern paleontologic ideas

Steno’s Laws Law of Superposition: younger strata lie above older strata Law of Horizontality: sedimentary strata were originally deposited horizontally Law of Lateral Continuity: sedimentary strata originally extended in all directions

James Hutton ( ) Salisbury Craigs (veins, baked contacts) Heat source deep within the Earth

James Hutton ( ) Siccar’s point Angular unconformity Rock cycle Subsidence Deposition Uplift and Deformation Weathering Erosion

Law of Faunal Succession 1841 Alcide d´Orbigny Concept of Stage 1856 Carl Albert Oppel - Concept of Biozone

Principle of Faunal Succession and Steno’s Laws

Charles Lyell ( ) Principles of Geology wwwwww.esp.org/books/lyell/principles/facsmile/contents.htm

Charles Lyell ( ) First relative geological time scale (1839) Fossil succession Laws of Steno

Geological Time Scale Gradstein et al. (2004) GTS2004 Neogene: based on astronomical ages Paleogene: based on radio-isotopic ages

Geological Time: dates and rates Tools: Biostratigraphy Lithostratigraphy Magnetostratigraphy Astrochronology Isotopic dating Aims: Global events Synchrony-diachrony Marine-continental Event stratigraphy

Stratigraphic correlations LithostratigraphicChronostratigraphicBiostratigraphic

Chronostratigraphy Biostratigraphy Lithostratigraphy

Magnetostratigraphy

Magnetostratigraphy a dipole reversing at irregular times

Geomagnetic time scales

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

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

Marine magnetic anomalies

Pitman and Heirtzler, 1966

Marine Magnetic Anomalies Deep Sea Cores vs.

Developing the GPTS

World crustal age Marine magnetic anomalies

Pre-Jurassic magnetostratigraphy Pangea From sen/nbcp/projectdescription.html

Pre-Jurassic magnetostratigraphy Position Newark Basin on Pangea From sen/nbcp/projectdescription.html

Pre-Jurassic magnetostratigraphy

Triassic-Jurassic geochronology: Magnetostratigraphy and Cyclostratigraphy Astronomical time scale for the Late Triassic based on Newark Basin Pre-Jurassic magnetostratigraphy

Triassic magnetostratigraphy … beyond the sea floor record

Even older: magneto- stratigraphy ?

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

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

Magnetostratigraphy Pitfalls and problems Only significant magnetostratigraphic dating if: unique pattern fit!

Ages GPTS not independent of other dating techniques

The times they are a-changing’ Bob Dylan 1964 Ages change with time …

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

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

Astronomical Polarity Time Scale (APTS) for the Mediterranean Neogene

Astronomical Time Scales

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

Milankovitch cycles

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

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

GTS2012

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

PONTIAN Acc. rate in C3r = 137cm/kyr Periodicity 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

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

ATNTS2012 in GTS2012 the successor of ATNTS2004

Independent dating methods Radio-isotope dating based on Radio-active decay Astronomical dating based on Orbital parameters ?=?=

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

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

Problem Offset ~1% Kuiper et al., 2008

Astrochronology Problems: Cycle recognition Phase relation Correlation Astronomical solution

La93 <> La2004

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

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

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 Ma

Age and uncertainty for FCT FCs = ± Ma

What about U/Pb FC? Wotzlaw et al.,2014

Magnetostratigraphy Possibilities, pitfalls and applications