Inclination Shallowing in Sedimentary Rocks: Evidence, Mechanism and Cause - Paleomagnetism of Sedimentary Rocks: Process and Interpretation - page 42

Table 4.1 Magnetite-bearing sediments and sedimentary rocks
Locality Lithology f factor Reference

North Atlantic deep-sea
sediments

Carbonate-rich ( > 80%) marine beds 0.48 Celaya & Clement (1988)

Gulf of Mexico marine sediments Clay-rich marine sediments 0.62 Sager & Singleton (1989)

Pacifi c marine sediments, DSDP
578

Biosiliceous clay, marine sediments 0.75 Arason & Levi (1990)

Hawaiian lake sediments Laminated silt and clay, lake sediments 0.82 Hagstrum & Champion

(1995), Peng & King (1992)

Great Bahama Reef Shallow marine carbonate sediments 0.84 McNeill (1997)

Dead Sea Lake sediments 0.45 Marco et al . (1998)

Pleistocene tephra in Japan Water-laid tephra 0.8 Iwaki & Hayashida (2003)

London Clay, Sheppey, England Eocene mudstones 0.63

Ali et al . (2003)

Sicak Cermik geothermal fi eld,
Turkey

Bedded travertine 0.68 Piper et al . (2007)

Yezo Group, Cretaceous Japan Marine sandstones and shales 0.71 Tamaki & Itoh (2008)

Yezo Group Cretaceous Japan Marine sandstones and shales 0.71 Tamaki et al . (2008)

Early Cretaceous limestones,
southern Alps

Marine limestones 0.89 Channell et al . (2010)

Donbas fold belt, Ukraine Carboniferous marine limestones (uC/

Permian red sandstones-not corrected)

0.65 Meijers et al . (2010a)

Average for Magnetite-bearing
sediments and rocks

0.69 ± 0.13 Bilardello & Kodama (2010b)

N = 13 f = 0.65 + 0.14/-0.11, N = 9

Freshwater lake sediments have also been observed
to enjoy signifi cant inclination shallowing. Hagstrum
& Champion (1995) were able to make a direct com-
parison of the inclinations recorded by lava fl ows and
lake sediments in Hawaii over the past 4400 years. The
expected geomagnetic axial dipole (GAD) fi eld has an
inclination of 35° and the lava fl ows recorded an
average inclination of 32°; in contrast, the lake sedi-
ments had low inclinations of c. 27 ° ( f = 0.73). Diver-
gence between the lake sediment inclination and the
expected inclination with depth in the lake core sug-
gests that compaction is the cause.
Marco et al . (1998) studied the paleomagnetism of
a core from Dead Sea lake sediments. At the bottom of
the 27 m long core, inclinations were 22° shallower
than the GAD fi eld ( f = 0.45). In the top 7 m of the core,
however, the inclinations were steeper than the GAD
fi eld. The shallowing trend with depth again supports
compaction as the cause of inclination shallowing in
these saline lake sediments.

Ancient sedimentary rocks with magnetite also
show evidence of inclination shallowing. Ali et al .
(2003) saw shallowing in the Eocene mudstones of the
London Clay Formation in Sheppey, England, with a
magnitude f equal to 0.57-0.69 depending on which
Eocene paleomagnetic pole provides the expected GAD
fi eld for comparison. Ali et al . also compared their
results to the coeval and nearby marine sediments of
DSDP Hole 550 and also observed shallowing in the
marine sediments. Tamaki & Itoh (2008) and Tamaki
et al . (2008) used the isothermal remanent magnetiza-
tion (IRM) correction technique of Hodych & Buchan
(1994; see next chapter for details of this technique) to
identify inclination shallowing in the Cretaceous Yezo
Group marine shales and sandstones from Hokkaido,
Japan ( f = 0.71). Their work indicates that the Yezo
Group is still anomalously shallow after inclination
correction, supporting 3400 km of northward motion
since the Campanian. Channell et al . (2010) calibrated
the magnetostratigraphy of Early Cretaceous lime-