De Verborgen Attractie van de Aarde

De Verborgen Attractie van de Aarde Opzet van de cursus 1 - Magnetisme & Aardmagneetveld 2 – Het Aardmagneetveld in het verleden 3 – Drift der Continenten en Plaattektoniek (4 – toepassingen) 5 – Omkeringen van het Aardmagneetveld (6 - toepassingen) 7 – Gesteentemagnetisme en (paleo)intensiteit van het veld 8 – Gastlezing & bezoek Fort Hoofddijk

De Verborgen Attractie van de Aarde Opzet van de cursus 1 - Magnetisme & Aardmagneetveld 2 – Het Aardmagneetveld in het verleden 3 – Drift der Continenten en Plaattektoniek (4 – toepassingen) 5 – Omkeringen van het Aardmagneetveld (6 - toepassingen) 7 – Gesteentemagnetisme en (paleo)intensiteit van het veld 8 – Gastlezing & bezoek Fort Hoofddijk

Stratigrafie Nicolaus Steno (1638-1686): Wet van superpositie Principe van horizontaal in origine Wet van laterale continuïteit Animated. One person per click. stratigraphy: the study of the sequence of strata (stratification), applied particularly to sedimentary and volcanic rocks Danish, pioneer in geology and anatomy, bishop Scottish, first modern scientific geologist Father of English Geology

Stratigrafie Nicolaus Steno (1638-1686): James Hutton (1726-1797): Wet van superpositie Principe van horizontaal in origine Wet van laterale continuïteit James Hutton (1726-1797): Uniformitarianisme Animated. One person per click. stratigraphy: the study of the sequence of strata (stratification), applied particularly to sedimentary and volcanic rocks Danish, pioneer in geology and anatomy, bishop Scottish, first modern scientific geologist Father of English Geology Uniformitarianism is the principle or assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe: ‘the present is the key to the past’

Stratigrafie Nicolaus Steno (1638-1686): James Hutton (1726-1797): Wet van superpositie Principe van horizontaal in origine Wet van laterale continuïteit James Hutton (1726-1797): Uniformitarianisme William Smith (1769-1831): Eerste geologische kaart van Engeland Gidsfossiel Animated. One person per click. stratigraphy: the study of the sequence of strata (stratification), applied particularly to sedimentary and volcanic rocks Danish, pioneer in geology and anatomy, bishop Scottish, first modern scientific geologist Father of English Geology

Stratigrafie George Cuvier (1769-1832) Charles Darwin (1809-1882) Taxonomie Uitsterven van soorten Charles Darwin (1809-1882) On the origin of species Ernest Rutherford (1871-1931) Absoluut dateren dmv. radiometrische technieken Animated. One person per click French zoologist, naturalist English naturalist New Zealand chemist and physicist who became known as the father of nuclear physics

Stratigrafie Methodes & Technieken - Lithostratigrafie – gesteente opeenvolgingen – Biostratigrafie – (gids)fossielen en hun evolutie – Magnetostratigrafie – omkeringen van het aardmagneetveld - Chemostratigrafie – kenmerkende chemische eigenschappen - Tectonostratigrafie – effecten van tektoniek – Cyclostratigrafie – herkennen Milankovitch cycli + absoluut dateren  chronostratigrafie Animated. Tools tekstbox appears on click chronostratigraphy (absolute) vs. relative dating Magnetostratigraphy is part of integrated stratigraphy!

Integrated Stratigraphy Biostratigrafie: first-order chronology taxonomie, reworking, diachroniteit ouderdom redelijk bekend vanaf Cambrium (500 Ma) Magnetostratigrafie: globally synchronous barcode primair vs. secondair signaal (overprint), correlatie, hiaten ? sequentie goed bekend voor laatste 200 Myr Cyclostratigrafie: fine-tuning and astronomical dating herkenning cycli, fase relaties, correlatie ouderdom t/m astronomical solutions (< 40 Ma) Animated. Per click one item.

Omkeringen van het aardmagneetveld Het aardmagneetveld keert op onregelmatige tijden om De meest karakteristieke eigenschap van de geodynamo … op onregelmatige tijden: maar wanneer dan ?

Oorsprong van omkeringen 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 300-500 yr Geodynamo action: Secular variation, excursions, reversals Animated. Picture with textboxes appears on click.

Geomagnetic Polarity Time Scale (GPTS) Constructie van de GPTS Hoe weten we het patroon en de ouderdommen van omkeringen ? Omkeringen magneetveld in lavas Brunhes (1906) - Matuyama (1921) Brunhes = present normal polarity chron Matuyama = last reversed polarity chron Animated. Picture and black text appears on click. Bernard Brunhes, Motonori Matuyama in France in 1905 opposite direction (reversed), in Japan in 1929 recognized the Brunhes-Matuyama reversal Brunhes=current normal (C1n), Matuyama=last reversed 2.58-0.78 Ma C1r). first reversals were thought to be the result of lightning strikes, self reversal (rare, less than 1% of all reversed igneous rocks) or reversal of geomagnetic field took another 50 yr to become fully expected navy and research vessels, exciting times discovery of ridges in 1872 while investigating future location of telegraph cables, confirmed by sonar in 1925, 1950’s mapping of ridges

Constructie GPTS – dateren lavas - Absolute dating by isotopic techniques in 1960s (eg. K/Ar) (Cox et al., 1964) Not animated. construction GPTS started in 1960s after 1970s improvement by continental sections with K-Ar dated volcanics (except for 0-4 Ma on Iceland)

Constructie GPTS – dateren lavas Not animated

Marine magnetic anomalies

Marine magnetic anomalies

Pitman and Heirtzler, 1966

Constructie GPTS Combineer: - Radiometrische dateringen van lavas (K/Ar) - Patroon van marine magnetische anomalieën Eerste versie: - Calibratiepunt (3.4 Ma) + extrapolatie op basis van constante spreiding Assuming constant seafloor spreading rate Not animated. Iceland allowed dating last 5 Myrs date ages of magnetic reversals simply by measuring the distance of successive magnetic anomalies from ridge axis The first geomagnetic polarity time scale to use marine magnetic anomalies as its primary data base was that of Heirtzler et al. (1968) in South Atlantic (by assuming constant sea-floor spreading rate from known GPTS of last 4 Myr), extrapolation by assuming constant spreading rate, only 5 myr difference at 70 Ma! Heirtzler et al. (1968)

Marine Magnetic Anomalies Deep Sea Cores vs.

deep-sea core drilling Constructie GPTS Redelijk bevestigd door: deep-sea core drilling plus biostratigrafie Not animated. DSDP by Glomar Challenger (1964-1983), ODP by JOIDES Resolution (1985-2003) and IODP by JOIDES Resolution and Chikyu (2007-recent) Testing the predicted ages of these polarity chrons was a major objective of the Deep Sea Drilling Project (DSDP). Marine sediments accumulate on newly generated oceanic crust. The age of the oldest sediment thus approximates the age of the oceanic crust. Paleontological dating of DSDP sediment cores provided “spot checks” on the polarity time scale. Magnetostratigraphic investigations of marine sedimentary sequences also have provided detailed biostratigraphic calibrations. Opdyke et al. (1966)

Constructie GPTS A new geomagnetic polarity time scale for the late Cretaceous and Cenozoic (Cande & Kent, 1992) Not animated. Langereis et al. (2010) figure 4b. En snapshot world magnetic anomaly map.

Constructie GPTS 9 calibratiepunten  interpolatie Volledige revisie MMA van alle oceanen 9 calibratiepunten  interpolatie CK1992 figure 18 and 27. Animated Another example from the Miocene. South Atlantic is the base. Faster spreading North Pacific correlated into the South Atlantic profile. Tiny wiggles – short lived geomagnetic phenomena only observed every now and then in fast-spreading oceanic plates – are superposed on category II anomalies. Age calibration very important: ages 0-5 Ma astronomically tuned!!

Constructie GPTS Steeds betere tuning … maar het kan altijd nòg beter Dankzij astronomical tuning ! Not animated.

Constructie GPTS Oudste sea-floor korst ~160 Ma Animated. 1 Lowrie & Oog 1986. 2) Lowrie 1997. Focus the latter on the part below the cretaceous long normal. Geomagnetic polarity time scale of Lowrie and Ogg (1986) for the Late Jurassic and Early Cretaceous. Marine Magnetic Anomalies are deep-towed.

Beyond the oldest sea-floor … Not animated. older reversals are based on continental records and questionable Triassic is primarily based on Newark APTS (USA), tuned by 400kyr eccentricity cycle, continental drill cores, red beds, but T/J is chosen, so not absolute age but relative age (to T/J) Tethyan Composite is the European scale correlation of Sicily and Slovak - magnetostratigraphy compared to GPTS

Constructie GPTS … en dan nòg ouder Not animated. - older reversals are based on continental records and questionable current status of knowledge Lower Cretaceous sucks! GTS 2012. Largest (chrono)stratigraphic knowledge gap in Phanerozoic Callovian (topmost Middle Jura, ~166 Ma) through Albian (topmost Early Cretaceous, ~100 Ma) Composite standard techniques for relative zone durations Radiometric ages unevenly spaced, fluctuating accuracy and precision: mathematical + statistical tools for calculating the geological time scale Stage boundaries are assigned error bars.

Nomenclatuur C11n.1n C11n.1r C11n.2n C18n.1r C18r Animated. Examples fly in. 1) C18r, 2) C11n.2n, 3) C11n.1n, 4) C11n.1r, 5) C18n.1r - polarity chrons: reversed and normal Chron number with n for normal and r for reversed, eg. C18r Subchrons are indicated by dots, eg. C18n.1r or C18n.2n C18r C-numbering nomenclature commonly used

Magnetostratigrafie Methode (piece of cake …) 1. Vind een mooie sectie 2. Boor en orienteer monsters 3. Meet de richtingen in het lab 4. Corrigeer voor laagstand 5. Gebruik de richtingen om polariteit te bepalen 6. Correleer het patroon naar GPTS Animated. Any pole position that is calculated from a single observation of the direction of the geomagnetic field is called a virtual geomagnetic pole (VGP). This is the position of the pole of a geocentric dipole that can account for the observed magnetic field direction at one location and at one point in time. Non-dipole field not averaged-out as for a paleomagnetic pole.

Magnetostratigrafie Streepjescode kan unieke correlatie geven - maar is essentieel binair - èn kan vervormd worden Problemen te over … - correlatie uniek ? primair signaal of overprint ? resolution hoog genoeg ? etcetera …. Animated. Barcodes appear a little later by themselves. Potential problems textbox appears on click. Magnetostratigraphy is utmost important for its contribution to the geological time scale but relies on other dating techniques (biostratigraphy, isotopic dating)

Magnetostratigrafie Magnetostratigrafisch dateren vereist een uniek patroon ? Animated. no reversal: single polarity zone without a base and top (11) one reversal (10) two reversals (9) correlation improves significantly if more than two reversals, however You date with the pattern, not with a single chron or a single reversal.

Correlatie Sedimentatiesnelheid onbekend of variabel Duur zones ? Hiaten ? Not animated. correlation of magnetostratigraphy of section in Chinese Tian Shan In the N7 zone a short reversed is not documented. Sampling resolution? Normal overprinting? The correlation of the N8 polarity zone is more or less entirely based on assumption sed rate = constant. It has little to do with pattern fitting. Authors are less certain of reversed periods, only one or two normals (in R0 and R8). There are probably more hiati than authors have considered. Conglomerates? Lithology? (Li et al., 2009)

Correlatie Afhankelijk van kwaliteit GPTS Verschillende methodes moeten overeenkomen Animated. Particularly if sections are short. Note the LaBreque 1977 time scale. Discrepancy between different dating techniques. In the APTS 2000 the discrepancy has been taken out. Anomaly pattern has been recalibrated. Magnetostratigraphy is utmost important for its contribution to the geological time scale but relies on other dating techniques: biostratigraphy, isotopic dating, astrochronology. It is part of the integrated stratigraphic approach. Fine-tuning if possible!

Voorbeeld: Betische Corridor Present Late Miocene Not animated. - first evaporites were thought to be part of MSC: magnetostratigraphy showed Tortonian Salinity Crisis! Krijgsman (2002) and Van Assen et al. (2006)

Voorbeeld Verschillende methodes kwamen niet overeen in 1998 K/Ar age: 6.16 ± 0.30 Ma Animated. 1) magneto age flies in 2) K/Ar age flies in. There is discrepancy. We’ll return to that later. Important for corralating Messinian strata through the region (southern Spain). Magneto age: 7.6 ± 0.1 Ma Garces et al. (1998)

Voorbeeld … again Garces et al. (2001) Verschillende methodes kwamen wèl overeen in 2001 Garces et al. (2001) K/Ar age: 6.16 ± 0.30 Ma Ar/Ar age: 7.71 ± 0.11 Ma Animated. 1) magneto age, 2) K/Ar age, 3) Ar/Ar age - first evaporites were thought to be part of MSC: magnetostratigraphy showed Tortonian Salinity Crisis! Magneto age: 7.6 ± 0.1 Ma

Radiometrisch dateren (K/Ar) Problemen: Bepalen fout in de meting Nauwkeurigheid vervalsconstante - Verlies van Ar (gas) bij 150 °C Absolute methode Dus òf goed òf jonger (zoals in voorbeeld) Not animated. known decay constant, ratio between the mother and daughter isotopes

Radiometrisch dateren (Ar/Ar) Ar/Ar ratio: mass spectrometer precision depends on e.g. measurement protocol, mass discrimination Decay constant Relatieve methode Not animated. - 40Ar* is derived from decay of 40K to 40Ar - disadvantage is that samples are radioactive and neutron flux irradiation undesired isotopic interferences need to be quantified by using a standard 1. in a nuclear reactor 39K is transformed into 39Ar by neutron capture, the concentration of 39Ar produced by irradiation is a function of 40K because 40K/39K is constant 2. laser But there is also air Ar contamination possible. Thus a spike 36Ar is used to constrain that. Newest generation mass spectrometers can tell apart 36Ar and 36Cl (isobaric interference is solved) so that spiking goes much more precise. J is an irradiation parameter and its accuracy depends on an accurately known age of a mineral standard.

Ar/Ar: mineral dating standard Kuiper et al., 2008 Animated. The Kuiper et al. (2008) curves appear on click. sanidine is a high temperature form of potassium feldspar Ar-Ar, 28.2 Ma, inter-laboratorty calibration by Kuiper et al. (2008) - Fish Canyon Tuff standard age, if this one used, no discrepancy with APTS, synchronizing rock clocks - VU Amsterdam, Berkeley Geochronology Center (USA)

Astronomical Polarity Time Scale (APTS) Animated. Frits appears

Astrochronology: correlation of cyclic variations in the geological record to computed astronomical (age) curves Not animated

Milankovitch cycles foutje Not animated

Milankovitch cycles in the Mediterranean Earth’s rotational and orbital motions determine changes in insolation and hence in climate and hence in environment and hence in the geological archive reflected in the sedimentary record Milutin Milankovitch (1879-1954)

Cycli & Astrochronologie Problemen: Herkennen cycli Fase relatie ? Correlatie Astronomisch model Not animated

Integrated stratigraphy: Bio-Magneto-Cyclostratigraphy Not animated. Hilgen et al. (2004)

Computed astronomical solutions min max Computed astronomical solutions

Astronomical solutions La93 <> La2004 Animated 2.5 Ma start; click 1) 7.5 Ma; click 2) 12.5 Ma.

Distance Season

Obliquity effect on Δtmax

Precession Today December: closest to Sun warm N-hemisphere winter hot S-hemisphere summer June: furthest from Sun cool N-hemisphere summer cold S-hemisphere winter

Precession ~11 kyr ago June: closest to Sun hot N-hemisphere summer warm S-hemisphere winter December: furthest from Sun cold N-hemisphere winter cool S-hemisphere summer

Tilt Season

Seasonal Contrast between N and S Hemispheres Small seasonal contrast Large seasonal contrast Distance Season Tilt Season

Sicily …

Sapropel-marl cycles of late Miocene age (Gibliscemi section, Sicily, Italy)

Sapropel Formation Insolation minimum = ARID Insolation maximum = HUMID

Computed astronomical solutions min max Computed astronomical solutions

400-kyr Eccentricity minimum Obliquity Insolation maximum Insolation minimum

400-kyr Eccentricity minimum Insolation maximum Insolation minimum Obliquity Carbonate cycles of early Pliocene age (Capo Bianco, Sicily, Italy)

Punta di Maiata, Sicily 400-kyr Eccentricity minimum Insolation maximum Punta di Maiata, Sicily

GPTS APTS Magnetostratigraphy: precise position of each geomagnetic reversal Geomagnetic Polarity Time Scale (GPTS): based on sea-floor magnetic anomaly patterns, ages interpolated between (few) calibration points Astronomically tuned Polarity Time Scale (APTS): accurate age of each individual reversal Hilgen, Langereis et al.

Miocene APTS Astrochronologie Laat Mioceen Secties op Kreta en Sicilië: ‘bed-to-bed’ correlatie Hilgen, Krijgsman, Langereis et al. (1995) Not animated

Punta di Maiata, Sicily

Lignite-marl cycles, Pliocene, Ptolemais section, Greece Insolation maximum Insolation minimum Lignite-marl cycles, Pliocene, Ptolemais section, Greece

40Ar/39Ar vs. astrochronology 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

Intercalibration Isotopic ages and astronomical ages Morocco Spain Cyclostratigraphy Ar/Ar ages of ash layers Spain Astronomical calibration Kuiper et al., 2008

Ar/Ar: mineral dating standard Kuiper et al., 2008 Animated. The Kuiper et al. (2008) curves appear on click. sanidine is a high temperature form of potassium feldspar Ar-Ar, 28.2 Ma, inter-laboratorty calibration by Kuiper et al. (2008) - Fish Canyon Tuff standard age, if this one used, no discrepancy with APTS, synchronizing rock clocks - VU Amsterdam, Berkeley Geochronology Center (USA)

Ar/Ar: mineral dating standard Animated. The Kuiper et al. (2008) curves appear on click. sanidine is a high temperature form of potassium feldspar Ar-Ar, 28.2 Ma, inter-laboratorty calibration by Kuiper et al. (2008) - Fish Canyon Tuff standard age, if this one used, no discrepancy with APTS, synchronizing rock clocks - VU Amsterdam, Berkeley Geochronology Center (USA) Kuiper et al. (2008), Science: 438 citaties

Magnetostratigrafie Animated. Title blok appears on click.

Van Waterschoot van der Gracht (1873-1948) Penning - 2014 Magnetostratigrafie Van Waterschoot van der Gracht (1873-1948) Penning - 2014