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Magnetic susceptibility cyclicity and magnetic dissolution in Cretaceous limestones of the southern Alps (Italy)
Author(s) -
Tarduno John A.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/92gl01484
Subject(s) - paleomagnetism , geology , remanence , cretaceous , polarity (international relations) , magnetostratigraphy , milankovitch cycles , paleontology , magnetite , magnetization , geomagnetic reversal , diagenesis , dissolution , magnetic susceptibility , mineralogy , chemistry , magnetic field , crystallography , biochemistry , physics , quantum mechanics , glacial period , cell
Sampling of a reversed polarity interval previously reported from limestones of the “Albian” Valle del Mis section (Southern Alps, Italy) indicates that it represents a recording of chron M3 of Barremian age rather than a brief reversed polarity ‘event’ in the Cretaceous Normal Polarity Superchron (K‐N). Hysteresis measurements suggest that magnetic susceptibility in these limestones is dominated by the paramagnetic clay fraction. Bulk magnetic susceptibility values exhibit a cyclicity which is correlated with the 100‐kyr Milankovitch eccentricity cycle. The stable record of reversed polarity is interrupted at six stratigraphically narrow intervals (< 1 m) by the apparent lack of any mineral having a stable remanent magnetization. I suggest these “paleomagnetic barren” intervals mark selective dissolution of magnetite related to increases in organic carbon. Such dissolution may explain some patterns of magnetization and re‐magnetization observed in world‐wide carbonates.