Apparent magnetic polarity reversals due to remagnetization resulting from late diagenetic growth of greigite from siderite
Author(s)
Roberts, A. P.
School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK
Weaver, R.
School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK
Verosub, K. L.
Department of Geology, University of California, Davis, CA 95616, USA
Pike, C. R.
3Department of Geology, University of California, Davis, CA 95616, USA
Clayton, T.
School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK
Wilson, G. S.
Department of Geology, University of Otago, Dunedin, New Zealand
Language
English
Obiettivo Specifico
2.2. Laboratorio di paleomagnetismo
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Issue/vol(year)
1 / 160 (2005)
Publisher
Blackwell Publishing
Pages (printed)
89-100
Date Issued
January 2005
Abstract
A mixed-polarity zone, representing alternations between remagnetized and non-remagnetized strata, has been documented within the lower few metres of the CRP-1 core (Ross Sea, Antarctica). Detailed rock magnetic investigation of this interval indicates that the normal polarity
remagnetization is carried by magnetostatically interacting single-domain particles of a ferrimagnetic iron sulphide mineral, while the reversed-polarity magnetization of non-remagnetized
strata is carried by magnetite with a broad range of grain sizes and negligible magnetostatic interactions. Scanning electron microscope observations of polished sections indicate that the ferrimagnetic iron sulphide mineral is greigite (Fe3S4). Based on microtextural relationships, it is not possible to determine the relative timing of formation for much of the greigite. However,
a significant proportion of the greigite has grown on the surface of authigenic siderite (FeCO3) grains that occur as microconcretions and as cement surrounding detrital matrix grains. In such cases, microtextural relationships indicate that siderite post-dates early diagenetic pyrite and that greigite post-dates the siderite. Siderite usually forms in environments with abundant
dissolved iron and carbonate, but without dissolved pore water H2S. This set of geochemical conditions occurs in methanic settings below the sulphate reduction zone (in which early diagenetic pyrite forms).We interpret the observed remagnetization of the lower part of the CRP-1 core as due to a late diagenetic pore water migration event where abundant iron on the surface of siderite grains reacted with fluids containing limited dissolved sulphide, thereby causing
precipitation of greigite. The distribution of siderite (and associated greigite) in the lower part of the CRP-1 core is patchy, which accounts for the apparent alternation of polarities. This study is part of a growing catalogue of remagnetizations involving greigite, which suggests that occurrences of greigite should be treated with caution in palaeomagnetic and environmental magnetic studies.
remagnetization is carried by magnetostatically interacting single-domain particles of a ferrimagnetic iron sulphide mineral, while the reversed-polarity magnetization of non-remagnetized
strata is carried by magnetite with a broad range of grain sizes and negligible magnetostatic interactions. Scanning electron microscope observations of polished sections indicate that the ferrimagnetic iron sulphide mineral is greigite (Fe3S4). Based on microtextural relationships, it is not possible to determine the relative timing of formation for much of the greigite. However,
a significant proportion of the greigite has grown on the surface of authigenic siderite (FeCO3) grains that occur as microconcretions and as cement surrounding detrital matrix grains. In such cases, microtextural relationships indicate that siderite post-dates early diagenetic pyrite and that greigite post-dates the siderite. Siderite usually forms in environments with abundant
dissolved iron and carbonate, but without dissolved pore water H2S. This set of geochemical conditions occurs in methanic settings below the sulphate reduction zone (in which early diagenetic pyrite forms).We interpret the observed remagnetization of the lower part of the CRP-1 core as due to a late diagenetic pore water migration event where abundant iron on the surface of siderite grains reacted with fluids containing limited dissolved sulphide, thereby causing
precipitation of greigite. The distribution of siderite (and associated greigite) in the lower part of the CRP-1 core is patchy, which accounts for the apparent alternation of polarities. This study is part of a growing catalogue of remagnetizations involving greigite, which suggests that occurrences of greigite should be treated with caution in palaeomagnetic and environmental magnetic studies.
References
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greigite) measured by AMS and partial AARM in weakly strained
sandstones from western Makran, Iran, Geophys. J. Int., 151, 729–737.
Baker, J.C.&Fielding, C.R., 1998. Diagenesis of glacimarine Miocene strata
in CRP-1, Antarctica, Terra Antartica, 5, 647–653.
Berggren, W.A., Kent, D.V., Swisher, C.C., III & Aubry, M.P., 1995. A
revised Cenozoic geochronology and biostratigraphy, in Geochronology,
Time Scales, and Stratigraphic Correlation,SEPMSpecial Publication 54,
pp. 129–212, eds Berggren, W.A., Kent, D.V., Aubry, M.P. & Hardenbol,
J., Society of Economic Paleontologists and Mineralogists, Tulsa, OK.
Berner, R.A., 1981. A new geochemical classification of sedimentary environments,
J. Sediment. Petrol., 51, 359–365.
Cande, S.C. & Kent, D.V., 1995. Revised calibration of the geomagnetic
polarity timescale for the Late Cretaceous and Cenozoic, J. geophys. Res.,
100, 6093–6095.
Cape Roberts Project Science Team, 1998. Initial report on CRP-1, Cape
Roberts Project, Antarctica, Terra Antartica, 5, 1–187.
Claps, M. & Aghib, F.S., 1998. Carbonate diagenesis in Miocene sediments
from CRP-1, Victoria Land Basin, Antarctica, Terra Antartica, 5, 655–
660.
Dekkers, M.J., 1988. Magnetic properties of natural pyrrhotite part I: behaviour
of initial susceptibility and saturation-magnetisation-related rockmagnetic
parameters in a grain-size dependent framework, Phys. Earth
planet. Inter., 52, 376–394.
Dekkers, M.J.&Schoonen, M.A.A., 1996. Magnetic properties of hydrothermally
synthesized greigite (Fe3S4)—I. Rock magnetic parameters at room
temperature, Geophys. J. Int., 126, 360–368.
De Santis, L. & Barrett, P.J., 1998. Grain size analysis of samples from
CRP-1, Terra Antartica, 5, 375–382.
Dinar`es-Turell, J.&Dekkers, M.J., 1999. Diagenesis and remanence acquisition
in the Lower PlioceneTrubi marls at Punta di Maiata (southern Sicily):
palaeomagnetic and rock magnetic observations, in Palaeomagnetism and
Diagenesis in Sediments, Geological Society of London Special Publication
151, pp. 53–69, eds Tarling, D.H. & Turner, P., Geological Society of
London, London.
Ellwood, B.B., Balsam, W., Burkart, B., Long, G.J. & Buhl, M.L., 1986.
Anomalous magnetic properties in rocks containing the mineral siderite:
paleomagnetic implications, J. geophys. Res., 91, 12 779–12 790.
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and associated pyrrhotite from Indiana, Am. Mineral., 42, 309–333.
Florindo, F. & Sagnotti, L., 1995. Palaeomagnetism and rock magnetism in
the upper Pliocene Valle Ricca (Rome, Italy) section, Geophys. J. Int.,
123, 340–354.
Frederichs, T., von Dobeneck, T., Bleil, U. & Dekkers, M.J., 2003. Towards
the identification of siderite, rhodochrosite, and vivianite in sediments by
their low-temperature magnetic properties, Phys. Chem. Earth, 28, 669–
679.
Furukawa, Y. & Barnes, H.L., 1996. Reactions forming smythite, Fe9S11,
Geochim. Cosmochim. Acta, 60, 3581–3591.
Harwood,D.M., Bohaty, S.M.&Scherer, R.P., 1998. LowerMiocene diatom
biostratigraphy of the CRP-1 drillcore, McMurdo Sound, Antarctica, Terra
Antarctica, 5, 499–514.
Hoffmann, V., Stanjek, H. & Murad, E., 1993. Mineralogical, magnetic and
M¨ossbauer data of smythite (Fe9S11), Stud. Geophys. Geodaet., 37, 366–
381.
Horng, C.-S.,Torii, M., Shea, K.-S.&Kao, S.-J., 1998. Inconsistent magnetic
polarities between greigite- and pyrrhotite/magnetite-bearing marine sediments
from the Tsailiao-chi section, southwestern Taiwan, Earth planet.
Sci. Lett., 164, 467–481.
Housen, B.A., Banerjee, S.K. & Moskowitz, B.M., 1996. Low-temperature
magnetic properties of siderite and magnetite in marine sediments, Geophys.
Res. Lett., 23, 2843–2846.
Howe, J.A., Woolfe, K.J. & Fielding, C.R., 1998. Lower Miocene glacimarine
gravity flows, Cape Roberts Drillhole-1, Ross Sea, Antarctica, Terra
Antartica, 5, 393–399.
Hu, S., Appel, E., Hoffmann, V., Schmahl, W.W. & Wang, S., 1998. Gyromagnetic
remanence acquired by greigite (Fe3S4) during static three-axis
alternating field demagnetization, Geophys. J. Int., 134, 831–842.
Ihml´e, P.F., Hirt, A.M. & Lowrie, W., 1989. Inverse magnetic fabric in deformed
limestones of the Morcles nappe, Switzerland, Geophys. Res. Lett.,
16, 1383–1386.
Jacobs, I.S., 1963. Metamagnetism of siderite (FeCO3), J. Appl. Phys., 34,
1106–1107.
Jiang,W.T., Horng, C.S., Roberts, A.P. & Peacor, D.R., 2001. Contradictory
magnetic polarities in sediments and variable timing of neoformation of
authigenic greigite, Earth planet. Sci. Lett., 193, 1–12.
Krs, M., Nov´ak, F., Krsov´a, M., Pruner, P., Koukl´ıkov´a, L. & Jansa, J., 1992.
Magnetic properties and metastability of greigite-smythite mineralization
in brown-coal basins of the Krusn´e Hory Piedmont, Bohemia, Phys. Earth
planet. Inter., 70, 273–287.
Krupp, R.E., 1994. Phase relations and phase transformations between the
low-temperature iron sulphides mackinawite, greigite, and smythite, Eur.
J. Mineral., 6, 265–278.
Lavelle, M., 1998. Strontium-isotope stratigraphy of the CRP-1 drillhole,
Ross Sea, Antarctica, Terra Antartica, 5, 691–696.
Lowrie, W., 1990. Identification of ferromagnetic minerals in a rock by
coercivity and unblocking temperature properties, Geophys. Res. Lett.,
17, 159–162.
McIntosh, W.C., 1998. 40Ar/39Ar geochronology of volcanic clasts and
pumice in CRP-1 core, Cape Roberts, Antarctica, Terra Antartica, 5, 683–
690.
Nov´ak, F. & Jansa, J., 1992. Authigenic smythite and pyrrhotite in the upper
part of the Sokolov Formation (the Sokolov Basin, Czechoslovakia), Bull.
Geol. Surv. Prague, 67, 235–244.
Oda, H. & Torii, M., 2004. Sea-level change and remagnetization of continental
shelf sediments off New Jersey (ODP Leg 174A): magnetite and
greigite diagenesis, Geophys. J. Int., 156, 443–458.
Pan, Y., Zhu, R. & Banerjee, S.K., 2000. Rock magnetic properties related
to thermal treatment of siderite: behavior and interpretation, J. geophys.
Res., 105, 783–794.
Pike, C.R., Roberts, A.P.&Verosub, K.L., 1999. Characterizing interactions
in fine magnetic particle systems using first order reversal curves, J. Appl.
Phys., 85, 6660–6667.
Postma, D., 1977. The occurrence and chemical composition of recent Ferich
mixed carbonates in a river bog, J. Sediment. Petrol., 47, 1089–1098.
Potter, D.K. & Stephenson, A., 1988. Single-domain particles in rocks and
magnetic fabric analysis, Geophys. Res. Lett., 15, 1097–1100.
Pye, K., 1981. Marshrock formed by iron sulphide and siderite cementation
in saltmarsh sediments, Nature, 294, 650–652.
Pye, K., Dickson, J.A.D., Schiavon, N., Coleman, M.L. & Cox, M., 1990.
Formation of siderite-Mg-calcite-iron sulphide concretions in intertidal
marsh and sandflat sediments, north Norfolk, England, Sedimentology,
37, 325–343.
Raiswell, R., 1997. A geochemical framework for the application of stable
sulphur isotopes to fossil pyritization, J. geol. Soc. Lond., 154, 343–356.
Raiswell, R. & Fisher, Q.J., 2000. Mudrock-hosted carbonate concretions: a
reviewof growth mechanisms and their influence on chemical and isotopic
composition, J. geol. Soc. Lond., 157, 239–251.
Richter, C., Roberts, A.P., Stoner, J.S., Benning, L.D. & Chi, C.T., 1998.
Magnetostratigraphy of Pliocene–Pleistocene sediments from the eastern
Mediterranean Sea, Proc. ODP, Sci. Res., 160, 61–74.
Rickard, D.T., 1968. Synthesis of smythite-rhombohedral Fe3S4, Nature,
218, 356–357.
Roberts, A.P., 1995. Magnetic properties of sedimentary greigite (Fe3S4),
Earth planet. Sci. Lett., 134, 227–236.
Roberts, A.P., Wilson, G.S., Florindo, F., Sagnotti, L., Verosub, K.L. &
Harwood, D.M., 1998. Magnetostratigraphy of lower Miocene strata from
the CRP-1 core, McMurdo Sound, Ross Sea, Antarctica, Terra Antartica,
5, 703–713.
Roberts, A.P., Pike, C.R.&Verosub, K.L., 2000. FORC diagrams: a newtool
for characterizing the magnetic properties of natural samples, J. geophys.
Res., 105, 28 461–28 475.
Rochette, P., 1988. Inverse magnetic fabric in carbonate-bearing rocks, Earth
planet. Sci. Lett., 90, 229–237.
Rochette, P., Jackson, M. & Aubourg, C., 1992. Rock magnetism and the
interpretation of anisotropy of magnetic susceptibility, Rev. Geophys., 30,
209–226.
Sagnotti, L. & Winkler, A., 1999. Rock magnetism and palaeomagnetism
of greigite-bearing mudstones in the Italian peninsula, Earth planet. Sci.
Lett., 165, 67–80.
Sagnotti, L., Florindo, F.,Wilson, G.S., Roberts, A.P.&Verosub, K.L., 1998.
Environmental magnetism of lower Miocene strata from the CRP-1 core,
McMurdo Sound, Antarctica, Terra Antartica, 5, 661–667.
Snowball, I.F., 1997a. Gyroremanent magnetization (GRM) and the magnetic
properties of greigite bearing clays in southern Sweden, Geophys. J.
Int., 129, 624–636.
Snowball, I.F., 1997b. The detection of single-domain greigite (Fe3S4) using
rotational remanent magnetization (RRM) and the effective gyro field
(Bg): mineral magnetic and palaeomagnetic applications, Geophys. J. Int.,
130, 704–716.
Stephenson, A., 1980a. Gyromagnetism and the remanence acquired by a
rotating rock in an alternating field, Nature, 284, 48–49.
Stephenson, A., 1980b. A gyroremanent magnetization in anisotropic magnetic
material, Nature, 284, 49–51.
Stephenson, A., 1993. Three-axis static alternating-field demagnetization of
rocks and the identification of NRM, GRM, and anisotropy, J. geophys.
Res., 98, 373–381.
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greigite) measured by AMS and partial AARM in weakly strained
sandstones from western Makran, Iran, Geophys. J. Int., 151, 729–737.
Baker, J.C.&Fielding, C.R., 1998. Diagenesis of glacimarine Miocene strata
in CRP-1, Antarctica, Terra Antartica, 5, 647–653.
Berggren, W.A., Kent, D.V., Swisher, C.C., III & Aubry, M.P., 1995. A
revised Cenozoic geochronology and biostratigraphy, in Geochronology,
Time Scales, and Stratigraphic Correlation,SEPMSpecial Publication 54,
pp. 129–212, eds Berggren, W.A., Kent, D.V., Aubry, M.P. & Hardenbol,
J., Society of Economic Paleontologists and Mineralogists, Tulsa, OK.
Berner, R.A., 1981. A new geochemical classification of sedimentary environments,
J. Sediment. Petrol., 51, 359–365.
Cande, S.C. & Kent, D.V., 1995. Revised calibration of the geomagnetic
polarity timescale for the Late Cretaceous and Cenozoic, J. geophys. Res.,
100, 6093–6095.
Cape Roberts Project Science Team, 1998. Initial report on CRP-1, Cape
Roberts Project, Antarctica, Terra Antartica, 5, 1–187.
Claps, M. & Aghib, F.S., 1998. Carbonate diagenesis in Miocene sediments
from CRP-1, Victoria Land Basin, Antarctica, Terra Antartica, 5, 655–
660.
Dekkers, M.J., 1988. Magnetic properties of natural pyrrhotite part I: behaviour
of initial susceptibility and saturation-magnetisation-related rockmagnetic
parameters in a grain-size dependent framework, Phys. Earth
planet. Inter., 52, 376–394.
Dekkers, M.J.&Schoonen, M.A.A., 1996. Magnetic properties of hydrothermally
synthesized greigite (Fe3S4)—I. Rock magnetic parameters at room
temperature, Geophys. J. Int., 126, 360–368.
De Santis, L. & Barrett, P.J., 1998. Grain size analysis of samples from
CRP-1, Terra Antartica, 5, 375–382.
Dinar`es-Turell, J.&Dekkers, M.J., 1999. Diagenesis and remanence acquisition
in the Lower PlioceneTrubi marls at Punta di Maiata (southern Sicily):
palaeomagnetic and rock magnetic observations, in Palaeomagnetism and
Diagenesis in Sediments, Geological Society of London Special Publication
151, pp. 53–69, eds Tarling, D.H. & Turner, P., Geological Society of
London, London.
Ellwood, B.B., Balsam, W., Burkart, B., Long, G.J. & Buhl, M.L., 1986.
Anomalous magnetic properties in rocks containing the mineral siderite:
paleomagnetic implications, J. geophys. Res., 91, 12 779–12 790.
Erd, R.C., Evans, H.T. Jr,&Richter,D.H., 1957.Smythite, a newiron sulfide,
and associated pyrrhotite from Indiana, Am. Mineral., 42, 309–333.
Florindo, F. & Sagnotti, L., 1995. Palaeomagnetism and rock magnetism in
the upper Pliocene Valle Ricca (Rome, Italy) section, Geophys. J. Int.,
123, 340–354.
Frederichs, T., von Dobeneck, T., Bleil, U. & Dekkers, M.J., 2003. Towards
the identification of siderite, rhodochrosite, and vivianite in sediments by
their low-temperature magnetic properties, Phys. Chem. Earth, 28, 669–
679.
Furukawa, Y. & Barnes, H.L., 1996. Reactions forming smythite, Fe9S11,
Geochim. Cosmochim. Acta, 60, 3581–3591.
Harwood,D.M., Bohaty, S.M.&Scherer, R.P., 1998. LowerMiocene diatom
biostratigraphy of the CRP-1 drillcore, McMurdo Sound, Antarctica, Terra
Antarctica, 5, 499–514.
Hoffmann, V., Stanjek, H. & Murad, E., 1993. Mineralogical, magnetic and
M¨ossbauer data of smythite (Fe9S11), Stud. Geophys. Geodaet., 37, 366–
381.
Horng, C.-S.,Torii, M., Shea, K.-S.&Kao, S.-J., 1998. Inconsistent magnetic
polarities between greigite- and pyrrhotite/magnetite-bearing marine sediments
from the Tsailiao-chi section, southwestern Taiwan, Earth planet.
Sci. Lett., 164, 467–481.
Housen, B.A., Banerjee, S.K. & Moskowitz, B.M., 1996. Low-temperature
magnetic properties of siderite and magnetite in marine sediments, Geophys.
Res. Lett., 23, 2843–2846.
Howe, J.A., Woolfe, K.J. & Fielding, C.R., 1998. Lower Miocene glacimarine
gravity flows, Cape Roberts Drillhole-1, Ross Sea, Antarctica, Terra
Antartica, 5, 393–399.
Hu, S., Appel, E., Hoffmann, V., Schmahl, W.W. & Wang, S., 1998. Gyromagnetic
remanence acquired by greigite (Fe3S4) during static three-axis
alternating field demagnetization, Geophys. J. Int., 134, 831–842.
Ihml´e, P.F., Hirt, A.M. & Lowrie, W., 1989. Inverse magnetic fabric in deformed
limestones of the Morcles nappe, Switzerland, Geophys. Res. Lett.,
16, 1383–1386.
Jacobs, I.S., 1963. Metamagnetism of siderite (FeCO3), J. Appl. Phys., 34,
1106–1107.
Jiang,W.T., Horng, C.S., Roberts, A.P. & Peacor, D.R., 2001. Contradictory
magnetic polarities in sediments and variable timing of neoformation of
authigenic greigite, Earth planet. Sci. Lett., 193, 1–12.
Krs, M., Nov´ak, F., Krsov´a, M., Pruner, P., Koukl´ıkov´a, L. & Jansa, J., 1992.
Magnetic properties and metastability of greigite-smythite mineralization
in brown-coal basins of the Krusn´e Hory Piedmont, Bohemia, Phys. Earth
planet. Inter., 70, 273–287.
Krupp, R.E., 1994. Phase relations and phase transformations between the
low-temperature iron sulphides mackinawite, greigite, and smythite, Eur.
J. Mineral., 6, 265–278.
Lavelle, M., 1998. Strontium-isotope stratigraphy of the CRP-1 drillhole,
Ross Sea, Antarctica, Terra Antartica, 5, 691–696.
Lowrie, W., 1990. Identification of ferromagnetic minerals in a rock by
coercivity and unblocking temperature properties, Geophys. Res. Lett.,
17, 159–162.
McIntosh, W.C., 1998. 40Ar/39Ar geochronology of volcanic clasts and
pumice in CRP-1 core, Cape Roberts, Antarctica, Terra Antartica, 5, 683–
690.
Nov´ak, F. & Jansa, J., 1992. Authigenic smythite and pyrrhotite in the upper
part of the Sokolov Formation (the Sokolov Basin, Czechoslovakia), Bull.
Geol. Surv. Prague, 67, 235–244.
Oda, H. & Torii, M., 2004. Sea-level change and remagnetization of continental
shelf sediments off New Jersey (ODP Leg 174A): magnetite and
greigite diagenesis, Geophys. J. Int., 156, 443–458.
Pan, Y., Zhu, R. & Banerjee, S.K., 2000. Rock magnetic properties related
to thermal treatment of siderite: behavior and interpretation, J. geophys.
Res., 105, 783–794.
Pike, C.R., Roberts, A.P.&Verosub, K.L., 1999. Characterizing interactions
in fine magnetic particle systems using first order reversal curves, J. Appl.
Phys., 85, 6660–6667.
Postma, D., 1977. The occurrence and chemical composition of recent Ferich
mixed carbonates in a river bog, J. Sediment. Petrol., 47, 1089–1098.
Potter, D.K. & Stephenson, A., 1988. Single-domain particles in rocks and
magnetic fabric analysis, Geophys. Res. Lett., 15, 1097–1100.
Pye, K., 1981. Marshrock formed by iron sulphide and siderite cementation
in saltmarsh sediments, Nature, 294, 650–652.
Pye, K., Dickson, J.A.D., Schiavon, N., Coleman, M.L. & Cox, M., 1990.
Formation of siderite-Mg-calcite-iron sulphide concretions in intertidal
marsh and sandflat sediments, north Norfolk, England, Sedimentology,
37, 325–343.
Raiswell, R., 1997. A geochemical framework for the application of stable
sulphur isotopes to fossil pyritization, J. geol. Soc. Lond., 154, 343–356.
Raiswell, R. & Fisher, Q.J., 2000. Mudrock-hosted carbonate concretions: a
reviewof growth mechanisms and their influence on chemical and isotopic
composition, J. geol. Soc. Lond., 157, 239–251.
Richter, C., Roberts, A.P., Stoner, J.S., Benning, L.D. & Chi, C.T., 1998.
Magnetostratigraphy of Pliocene–Pleistocene sediments from the eastern
Mediterranean Sea, Proc. ODP, Sci. Res., 160, 61–74.
Rickard, D.T., 1968. Synthesis of smythite-rhombohedral Fe3S4, Nature,
218, 356–357.
Roberts, A.P., 1995. Magnetic properties of sedimentary greigite (Fe3S4),
Earth planet. Sci. Lett., 134, 227–236.
Roberts, A.P., Wilson, G.S., Florindo, F., Sagnotti, L., Verosub, K.L. &
Harwood, D.M., 1998. Magnetostratigraphy of lower Miocene strata from
the CRP-1 core, McMurdo Sound, Ross Sea, Antarctica, Terra Antartica,
5, 703–713.
Roberts, A.P., Pike, C.R.&Verosub, K.L., 2000. FORC diagrams: a newtool
for characterizing the magnetic properties of natural samples, J. geophys.
Res., 105, 28 461–28 475.
Rochette, P., 1988. Inverse magnetic fabric in carbonate-bearing rocks, Earth
planet. Sci. Lett., 90, 229–237.
Rochette, P., Jackson, M. & Aubourg, C., 1992. Rock magnetism and the
interpretation of anisotropy of magnetic susceptibility, Rev. Geophys., 30,
209–226.
Sagnotti, L. & Winkler, A., 1999. Rock magnetism and palaeomagnetism
of greigite-bearing mudstones in the Italian peninsula, Earth planet. Sci.
Lett., 165, 67–80.
Sagnotti, L., Florindo, F.,Wilson, G.S., Roberts, A.P.&Verosub, K.L., 1998.
Environmental magnetism of lower Miocene strata from the CRP-1 core,
McMurdo Sound, Antarctica, Terra Antartica, 5, 661–667.
Snowball, I.F., 1997a. Gyroremanent magnetization (GRM) and the magnetic
properties of greigite bearing clays in southern Sweden, Geophys. J.
Int., 129, 624–636.
Snowball, I.F., 1997b. The detection of single-domain greigite (Fe3S4) using
rotational remanent magnetization (RRM) and the effective gyro field
(Bg): mineral magnetic and palaeomagnetic applications, Geophys. J. Int.,
130, 704–716.
Stephenson, A., 1980a. Gyromagnetism and the remanence acquired by a
rotating rock in an alternating field, Nature, 284, 48–49.
Stephenson, A., 1980b. A gyroremanent magnetization in anisotropic magnetic
material, Nature, 284, 49–51.
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