Supplementary Information to accompany
Putative greigite magnetofossils from the Pliocene epoch
Iuliana Vasiliev, Christine Franke, Johannes D. Meeldijk, Mark J. Dekkers, Cor G.
Langereis, Wout Krijgsman
Guide to Supplementary Information
Supplementary Methods
Supplementary Palaeomagnetic and Rockmagetic Properties p. 2
Methods
Supplementary Microscopy Methods
p. 3
Geological setting and sedimentary environment
p. 4
Supplementary Figures and Legends
Supplementary Figure 1. Palaeogeography of the study area.
p. 5
Supplementary Figure 2. Gyroremanent magnetisation in p. 6
greigite.
Supplementary Figure 3. Greigite prismatic magnetofossil.
p. 7
Supplementary Figure 4. Magnetofossil greigite plotted on the p. 8
SD stability field of magnetite.
Supplementary Figure 5. Magnetite magnetofossils.
p. 9
Supplementary Figure 6. Palaeomagnetic and rock magnetic p. 10
measurements performed on sample RR 122.
Supplementary
Figure
7.
Characteristic
thermal p. 11
demagnetization behaviour.
Supplementary References cited in the supplementary information
1
© 2008 Macmillan Publishers Limited. All rights reserved.
Supplementary Methods: Palaeomagnetism and Rock Magnetism
To assess the magnetic mineralogy, we performed thermomagnetic runs in air with a
modified horizontal translation type Curie balance1 with a sensitivity of
approximately 5×10−9 Am2. Runs during different heating (solid lines) and cooling
(dashed lines) cycles were performed at a rate of 10 °C min-1. Approximately 70 mg
of powdered sample was put into a quartz glass sample holder held in place by quartz
wool. Total magnetization is plotted in a series of runs to increasingly higher
temperatures (100, 200, 300, 350, 450, 500 and 700 °C, respectively). Each six
seconds a data point was recorded, equivalent to one degree Celsius. The applied field
was cycled between 150 and 300 mT. An alternating gradient magnetometer
(Princeton Measurements Corporation, MicroMag Model 2900 with 2T magnet, noise
level 2×10−9 Am2) was used to successively measure hysteresis loops, FORC
diagrams, IRM acquisition (after having used the demagnetization option of the
MicroMag) and backfield demagnetization curves, all at room temperature. The
saturation magnetization (Ms), the saturation remanent magnetization (Mrs) and
coercive force (Bc) were determined from the measured hysteresis curves, after
applying the correction for the paramagnetic contribution on a mass-specific basis. To
further assess the magnetic domain state, the effects of magnetic interactions and the
magnetic mineralogy, FORC diagrams were measured2. IRM acquisition curves,
acquired with the MicroMag System, were decomposed into coercivity components
using the fitting program of Kruiver3, limited to symmetric distributions in the logspace. Palaeomagnetic results have been previously documented for the studied
sedimentary rocks4-7 and extensive rock magnetic investigations were presented
elsewhere7.
2
© 2008 Macmillan Publishers Limited. All rights reserved.
Supplementary Methods: Electron Microscopy
For TEM analyses, magnetic extracts were obtained using the extraction procedure
described by Dekkers8. The extraction was performed on 20 grams of grinded rock
samples. The resulting powders were well dispersed by ultrasonic agitation for forty
minutes
in
demineralised
argon-purged
water.
Sodium
polyphosphate
[Na4P2O7·10H2O] was used as a peptising agent to keep the clay mineral particles
dispersed. The obtained suspension was put on the extracting column for three hours.
The prolonged ultrasonic agitation was necessary because the rock samples were
strongly lithified clays. The resulting extracts were washed with demineralised water
in three steps using a ‘magnetic finger’9 to purify the grains from remaining clay
flakes. To further remove adhering clay mineral coatings we used the cleaning
procedure described by Franke et al.,10. After a second agitation in the ultrasonic bath
for another two minutes to disperse the magnetic concentrate, carbon coated TEM
copper grids were dipped into the extract and subsequently dried in air. For efficiency
we used a magnetic finger attached to the exterior of the vial that attracted the
particles mostly on one side of the copper grid. We took care not to attract too much
of the coarser particles. For all TEM analyses, a FEI Tecnai 20 FEG transmission
electron microscope was used at an acceleration voltage of 200 kV in bright field
mode, at high resolution, or for recording electron diffraction patterns. Elemental
compositions were identified by using energy dispersive spectroscopy.
3
© 2008 Macmillan Publishers Limited. All rights reserved.
Geological setting and sedimentary environment
The samples have been taken from riverbeds where the rock surfaces were freshly
cleaned by the stream. The sedimentary sequence consists of an alternation of blue to
grey sandstones, siltstones and clays. Our sections start stratigraphically in deposits of
late Sarmatian age and end at Romanian (Eastern Paratethys nomenclature11). In the
Supplementary Figure 1 we show the uppermost Miocene and Pliocene, greigitebearing, part of the section. The older (upper Miocene part) has magnetite as a
magnetic carrier. The appearance of greigite in Chron C3r (between 6.0 and 5.5 Ma)
is most likely related to regional tectonic and/or climatic events that reshaped the
basin configuration and consequently changed drastically the palaeoenvironmental
conditions. However, the presence of benthic ostracods12,13 and molluscs13,14
throughout the entire upper Miocene-Pliocene time interval demonstrates that the
lowermost water column remained sufficiently oxygenated for these organisms to
live. Anoxic conditions favouring greigite formation could therefore only have been
present within the sediments, related to degradation of organic matter during rapid
burial. Greigite formation in the Romanian Carpathian foredeep palaeoenvironment
occurred in a very high sedimentation rate setting (60-150 cm/kyr4), a situation
similar to south-western Taiwan15-18 and eastern New Zealand19,20. High
sedimentation rates accompanied by rapid burial of organic matter will lead to a
completely anoxic diagenetic environment close to the sediment/water interface21,22.
In such settings, the authigenic greigite in the Eastern Carpathian foredeep likely has
formed through bacterial mediation during early diagenesis, up to kyrs after
deposition.
4
© 2008 Macmillan Publishers Limited. All rights reserved.
0ºE
10ºW
20ºE
10ºE
40ºE
30ºE
60ºE
50ºE
55ºE
a
Panel b
Russia
Poland
Ukraine
Rimnicu Sarat Valley
(45.55ºN and 26.88ºE)
50ºE
V
7200
ol
g
a
7000
45ºE
Aral
n Se a
Turkey
40ºE
ea
nS
6600
6400
an
Mediterr
6800
a
spi
A tl a
Ca
Black Sea
C2An.1n
n ub e
35ºE
ea
km
0
Late Miocene/early Pliocene of the Paratethys
400
30ºE
800
6200
6000
5800
25ºE
5600
b
5400
Romanian
Da
ntic
Oc
e
an
France
5200
Germany
5000
Ukraine
4800
Hungary
C2Ar
4600
Romania
4400
ly
Black Sea
4000
C
3400
1100
950
Dacian
1000
N
3200
N
3000
2800
900
2600
850
2400
800
700
650
T
2000
550
C3r
1800
600
T
2200
Pontian
750
Pontian
Stratigraphic level (m)
Supplementary Figure. 1
Palaeogeography of the study area. (a) Schematic
palaeogeographic map of the late Miocene/early
Pliocene, showing the Paratethys area and the presentday land contribution; (b) map of the study areas
modified after Vasiliev et al., 20077 with the indication
the geographic position of the sections in front of the
Romanian Carpathians. The polarity zones with
palaeomagnetic data for the studied river sections:
Badislava and Rîmnicu Sarat. Black (white) denotes
normal (reversed) polarity. The indicatives for the most
important subchrons are displayed (C = Cochiti, S =
Sidufjall, N = Nunivak, T = Thvera). The names of the
substages are according to the Eastern Paratethys
nomenclature11. Mean latitudes and longitudes (in
decimal degrees) are given in the header of the
magnetostratigraphy columns.
1050
Dacian
3800
Badislava Valley
3600
(45.15ºN and 24.53ºE)
Turkey
1600
C3r
Ita
4200
Bulgaria
1400
180 360 -90 0 90
Declination Inclination
© 2008 Macmillan Publishers Limited. All rights reserved.
Meot.
180 360 -90 0 90
Declination Inclination
a
up/W
80
100 mT
90
BD110.1B b
BD114.1B
up/W
N
0 mT
Inti = 3 mAm-1
Inti = 11 mAm-1
N
60 70
80
100 mT
Supplementary Figure 2.
Gyroremanent magnetisation in greigite. (a) and (b) are tilt corrected Zijderveld
diagrams of typical alternating field (AF) demagnetisation behaviour; open (closed)
circles are projections on the vertical (horizontal) plane. Initial NRM intensities (Inti) are
given. The values represent milliTesla (mT). AF demagnetisation was performed by an
in-house developed robot, which let the samples pass-through a 2G Enterprises SQUID
magnetometer (noise level 10-12 Am2). After 45 mT AF demagnetisation, the samples
were increasingly acquiring a gyroremanent magnetisation much larger than the initial
NRM. (a) BD 110.1B is the sister sample of BD 110.1A (Fig. 1c); note the remarkable
difference between thermal and AF demagnetisation. (b) BD 114.1B is the sister sample
of BD 114.1A which has identical thermal demagnetisation behaviour as sample BD
115.1A (Fig. 1b).
© 2008 Macmillan Publishers Limited. All rights reserved.
a
Panel c
b
1 {200}
53 o
Panel d
2 {111}
6
o
8
3
{111}
Panel b
5 nm
20 nm
c
d
(111) 5
.7A
10 nm
10 nm
Supplementary Figure 3.
Greigite prismatic magnetofossil. (a) TEM micrograph of elongated prismatic
greigite crystal with well-defined truncated edges. There is non-uniform contrast
indicating changing thickness as expected from the outline of the crystal. (b) High
magnification of the area indicated in panel a. Three sets of lattice fringes: set 1
corresponds to the {200} plane, sets 2 and 3 correspond to the {111} plane. Set 2
forms angles of 68 º and 53 º with sets 3 and 1, respectively. (c) High
magnification of the lattice image of the area indicated in panel a. The bands
between the lines indicate a d-spacing of 5.7 Å, corresponding to (111) greigite
reflection. (d) High magnification of the lattice image from a truncated edge of the
crystal.
© 2008 Macmillan Publishers Limited. All rights reserved.
a
Multidomain
Length (nm)
300
Elongate
Irregular
Metastable
SD
Cuboidal
Stable
SD
100
Elongate
Prismatic
30
Superparamagnetic
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
Shape Factor (Width/Length)
b
200 nm
Supplementary Figure 4.
Magnetofossil greigite plotted on the SD
stability field of magnetite. (a) The diagram is
redrawn after Kopp and Kirschvink, 200723 and is
a function of shape factor (width/length ratio) and
length. For details see23. Shaded regions mark
size and shape of crystals from magnetotactic
bacteria. The shape fields in the diagram are based
upon the specific crystal morphologies produced by
living magnetite-producing magnetotactic bacteria,
not greigite-producing ones. The elongated
prismatic greigite crystals in our samples fit on the
cuboidal area of Kopp and Kirschvink23. We still
interpret them as prismatic because they are
different from the cuboctahedral crystals in our
samples. In addition, the cuboctahedral crystals are
smaller than all existing data so far. The
importance of the magnetic interaction at these
critical sizes has been shown to be very
important24. (b) TEM micrograph of a cluster of
cuboctahedral greigite crystals; (c) the size
distributions of the greigite crystals from panel b.
These measurements are subject to bias because,
at this size, even with the excellent resolution, it is
difficult to obtain the true size values of the crystals.
Therefore, we chose to count the particle three
times, then stacked these measurements (in total
443) and run the statistics. The mean size value of
the particles is 24.61 nm with 3.71 as standard
deviation. The histogram shows a clearly skewed
(to the left) distribution, which indicates a
magnetosomal origin of these crystals25,26.
c 0.25
Frequency
0.20
0.15
0.10
0.05
0.00
12 16 20 24 28 32 36 40
Particle lengh (nm)
© 2008 Macmillan Publishers Limited. All rights reserved.
a
100 nm
b
500
C
Counts (s-1)
400
300
200
Cu
100
Fe
O
Fe Si
Cu
Fe
0
0
1
2
3
4
5
6
Energy [keV]
7
8
9
10
Supplementary Figure 5.
Fossil magnetite magnetosomes. (a) TEM micrograph of prismatic magnetite
crystals. In the upper left part of the image they are aligned in a (disrupted) chain
and in the lower right part they are clustered in no preferred order. (b) Energydispersive X-ray spectrum from the crystals of the chain in the image showing
the distinct peaks for Fe and O of iron oxide. Al and Si peaks are caused by the
background signal of the clay mineral flake; the C and Cu peaks originate from
the carbon coated copper TEM grid.
© 2008 Macmillan Publishers Limited. All rights reserved.
Total magnetisation (Am2kg-1)
a
up/W
180 oC
210
Inti = 16 mAm-1
240
270
380
N
0.030
b
0.026
0.022
0.018
0.014
0.010
0.006
0
Am2kg-1)
c
0.8
0.2
8
100
200
300
400
e
1
200
300
400
Temperature (oC)
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
0
-0.1
50
SF = 3
40
30
Bu (mT)
20
10
0
-10
-20
-30
-40
-50
20
40
60
80
Bc (mT)
100
120
IRM (10-3 X Am2kg-1)
100
20
IRM (10-3 X Am2kg-1)
0
45
600
700
d
4
0
Bc = 28.8 mT
Bcr = 62.4 mT
Mr/Ms = 0.30
-4
-8
-300
0.0
500
Temperature (oC)
M
0.4
x
0.6
(10-3
Normalized intensity
1.0
0
f
16
300
B (mT)
Linear
Aquisition
Plot
12
8
4
0
1
10
100
Gradient
Aquisition
Plot
30
1000
B1/2 = 74.1 mT
DP = 0.11
magnetosomes
B1/2 = 74.1 mT
DP = 0.36
authigenic
15
0
1
10
100
1,000
Applied field (mT)
Supplementary Figure 6.
Palaeomagnetic and rock magnetic measurements performed on sample RR 122. (a) Zijderveld diagram (after tilt correction)
with the direction of the low (blue arrow) and high (red arrow) temperature component. Correspondingly coloured numbers are the
temperature steps taken to calculate the directions of the two temperature components. See also caption to figure 1. (b)
Thermomagnetic runs during different heating (red solid lines) and cooling (blue dashed lines) show an irreversible decrease in
magnetization caused by the greigite decomposition reaction chain, between 200 and 400 ºC. A slight increase in the total
magnetization is visible at ~500 ºC, indicating the formation of new magnetic minerals because of oxidation of an iron sulphide.
This temperature is higher than the ones known for alteration of iron sulphides. (c) Normalized decay curve represented as
absolute (blue diamonds) and difference vector sum (red circles) values. There are two major inflections in the decay curves
arising from the combined effect of greigite alteration and magnetic unblocking. These extrapolated lines (to ~290 ºC and ~350
ºC) indicate two magnetic carriers, represented by blue and red areas. The hatched area indicates a possibly viscous (e.g.
laboratory induced) magnetisation removed up to 100 ºC. (d) Hysteresis loop shown between ±300 mT. (e) FORC diagram,
indicating (highly interacting) SD particles. (f) IRM acquisition curve, decomposed into coercivity components using a log-normal
fitting program3. Open blue squares are measured data points. The components are marked with green and purple lines on the
linear acquisition plot (LAP) and equivalently coloured shading on the gradient acquisition plot (GAP). Both components have the
same coercivity (B1/2), but different dispersion parameters (DP) indicating different grain size distribution. For additional details,
see also the supplementary palaeomagnetic and rock magnetic methods section.
© 2008 Macmillan Publishers Limited. All rights reserved.
up/W
1.0
N
400
340
Inti = 2 mAm-1
240
Normalized intensity
a
RR 097
C2An.1n
~2.80 Ma
Gauss
0.8
0.6
0.4
0.2
0.0
20oC
No
390 C
20oC
100
200
300
400
1.0
up/W
Inti = 2 mAm-1
Normalized intensity
150
b
0
RM 034
C3An.1n
~6.05 Ma
0.8
0.6
0.4
0.2
0.0
0
150
210
Inti = 8 mAm-1
360
N
400
TP 22
C3r.2r
~4.70 Ma
0.6
0.4
0.2
180
240
100
200
1.0
up/W
Inti = 4 mAm-1
300
0.0
Normalized intensity
d
200
0.8
0
20oC
100
1.0
up/W
Normalized intensity
c
20oC
300
400
TP 12
C3n.4n
~4.99 Ma
Thvera
0.8
0.6
0.4
0.2
0.0
N
285-360
0
100
200
300
400
Temperature (oC)
Supplementary Figure 7.
Characteristic thermal demagnetization behaviour. On the left hand side of
each panel, Zijderveld diagrams are plotted after tilt correction. Blue and red
arrows as in caption to Supplementary Fig. 1. On the right hand side are the
corresponding normalized decay curves. We show examples from two valleys that
generated greigite-based magnetostratigraphy (RR and RM from Rîimnicu Sarat
and TP from Topolog sections). (a) Sample with different normal HT and LT
components showing a decay curve suggesting two main magnetic carriers for the
respective components; (b) sample showing dual polarity recorded within the same
sample at the transition from normal to reverse. The delayed LT component was
acquired during the later reversed field. From Topolog valley: (c) sample TP 22 was
magnetized in a reversed magnetic field and has again two distinguishable
components; (d) sample TP 12 shows dual polarity recorded within the same
sample at the reversal from normal to reversed.
© 2008 Macmillan Publishers Limited. All rights reserved.
Supplementary References
1.
Mullender, T. A. T., van Velzen, A. J. & Dekkers, M. J. Continuous drift
correction and separate identification of ferromagnetic and paramagnetic
contribution in thermomagnetic runs. Geophys. J. Int. 114, 663-672 (1993).
2.
Roberts, A. P., Pike, C. R. & Verosub, K. L. First-order reversal curve
diagrams: A new tool for characterising the magnetic properties of natural
samples. J. Geophys. Res. 102, 28461-28475 (2000).
3.
Kruiver, P. P., Dekkers, M. J. & Heslop, D. Quantification of the magnetic
coercivity components by the analysis of aquisition curves of isothermal
remanent magnetisation. Earth Planet. Sci. Lett. 189, 269-276 (2001).
4.
Vasiliev, I. et al. Towards an astrochronological framework for the eastern
Paratethys Mio-Pliocene sedimentary sequences of the Focsani basin
(Romania). Earth Planet. Sci. Lett. 227, 231-247 (2004).
5.
Vasiliev, I., Krijgsman, W., Stoica, M. & Langereis, C. G. Mio-Pliocene
magnetostratigraphy in the southern Carpathian foredeep and MediterraneanParatethys correlation. Terra Nova 17, 374-387 (2005).
6.
Dupont-Nivet, G., Vasiliev, I., Langereis, C. G., Krijgsman, W. & Panaiotu,
C. Neogene tectonic evolution of the southern and eastern Carpathians
constrained by paleomagnetism. Earth Planet. Sci. Lett. 236, 234-387 (2005).
7.
Vasiliev, I. et al. Early diagenetic greigite as a recorder of the palaeomagnetic
signal in Miocene–Pliocene sedimentary rocks of the Carpathian foredeep
(Romania). Geophys. J. Int. 171, 613-629 (2007).
8.
Dekkers, M. J. in Geologica Ultraietina 231 (Utrecht University, Utrecht,
1988).
12
© 2008 Macmillan Publishers Limited. All rights reserved.
9.
von Dobeneck, T., Petersen, N. & Vali, H. Baktrielle Magnetofossilen Palaomagnetische spuren einer ungewohlichen Bakteriengruppe.
Geowissenschaften in unserer Zeit 5, 27-35 (1987).
10.
Franke, C., Frederichs, T. & Dekkers, M. J. Efficiency of heavy liquid
separation to concentrate magnetic particles. Geophys. J. Int. 170, 1053-1066
(2007).
11.
Rögl, F. & Daxner-Hock, G. Late Miocene Paratethys Correlation. The
Evolution of the Western Eurasian Neogene Mammal Faunas, 487 (1996).
12.
Olteanu, R. in Pliozän Pl1 Dazien (eds. Marinescu, F. & Papaianopol, I.) 530
(Editura Academiei Romane, Bucharest, 1995).
13.
Stoica, M., Lazar, I., Vasiliev, I. & Krijgsman, W. Mollusc assemblages of the
Pontian and Dacian deposits from the Topolog-Arges area (southern
Carpathian foredeep - Romania). Geobios 40, 391-405 (2007).
14.
Papaianopol, I. in Chrostratigraphie und Neostratotypen 530 (Editute
Academiei Romane, Bucharest, 1995).
15.
Horng, C.-S., Chen, J.-C. & Lee, T.-Q. Variation in the magnetic minerals
from two Plio-Pleistocene marine-deposited sections, southwestern Taiwan. J.
Geol. Soc. China 35, 323-335 (1992).
16.
Horng, C.-S., Laj, C., Lee, T.-Q. & Chen, J.-C. Magnetic characteristics of
sedimentary rocks from the Tsengwen-chi and Erhjen-chi sections in
southwestern Taiwan. TAO 3, 519-532 (1992).
17.
Jiang, W.-T., Horng, C.-S., Roberts, A. P. & Peacor, D. R. Contradictory
magnetic polarities in sediments and variable timing of neoformation of
authigenic greigite. Earth Planet. Sci. Lett. 193, 1-12 (2001).
13
© 2008 Macmillan Publishers Limited. All rights reserved.
18.
Kao, S.-J., Horng, C.-S., Roberts, A. P. & Liu, K.-K. Carbon-sulfur-iron
relationships in sedimentary rocks from souwthwestern Taiwan: influence of
geochemical environment on greigite and pyrrhotite formation. Chem. Geol.
203, 153-168 (2004).
19.
Roberts, A. P. & Turner, G. M. Diagenetic formation of ferrimagnetic iron
sulphide minerals in rapidly deposited marine sediments, South Island, New
Zealand. Earth Planet. Sci. Lett. 115, 257-273 (1993).
20.
Rowan, C. J. & Roberts, A. P. Magnetite dissolution, diachronous greigite
formation, and secondary magnetizations from pyrite oxidation: unravelling
complex magnetizations in Neogene marine sediments from New Zealand.
Earth Planet. Sci. Lett. 241, 119-137 (2006).
21.
Westrich, J. T. & Berner, R. A. The role of sedimentary organic matter in
bacterial sulphate reduction: the G model tested. Limnol. Oceanogr. 29 (1984).
22.
Canfield, D. E. & Berner, R. A. Dissolution and pyritization of magnetite in
anoxic marine sediments. Geochim. Cosmochim. Acta 51, 645-659 (1987).
23.
Kopp, R. E. & Kirschvink, J. L. The identification and biogeochemical
interpretation of fossil magnetotactic bacteria. Earth Sci. Rev. 86, 42-61
(2007).
24.
Muxworthy, A. R. & Williams, W. Critical single-domain/multidomain grain
sizes in noninteracting and interacting elongated magnetite particles:
Implications for magnetosomes. J. Geophys. Res. 111,
doi:10.1029/2006JB004588 (2006).
25.
Posfai, M. et al. Crystal-size distributions and possible biogenic origin of Fe
sulfides. Eur. J. Mineral. 13, 691-703 (2001).
14
© 2008 Macmillan Publishers Limited. All rights reserved.
26.
Kruiver, P. P. & Passier, H. F. Coercivity analysis of aquisition curves of
magnetic phases in sapropel S1 related to variation in redox conditions,
including an investigation of the S-ratio. Geochem. Geophys. Geosyst. Art.
number 2001GC000181 (2001).
15
© 2008 Macmillan Publishers Limited. All rights reserved.