Geology Reference
In-Depth Information
250
200
150
100
50
S
N
0
-200
-150
-100
-50
0
50
100
Distance (m)
150
200
-50
-100
-150
Figure 12.1.5. Magnetic edge effect of a clinker layer, assuming magnetization typical for North Dakota samples
(Sternberg and Lippincott (2004)). The depth to the top of the clinker is 5 m, and the thickness of the clinker layer
is also 5 m. The clinker occupies the half-plane to the south of zero on the horizontal axis, adjoining unbaked
sediments to the north of zero.
known magnetizations, could also allow the separation of different magnetic sources (Khesin and Itkis, 2002), such as
older clinkers and younger surface burns.
Although not stressed here, the ability of pyrometamorphic rocks to acquire a remanent magnetization makes them
potentially useful for paleomagnetic studies of field direction (Jones et al, 1984; Lindqvist et al., 1985; Parse and
Sternberg, 1989; Radan and Radan, 1998; de Boer et al., 2001) and field strength, or paleointensity (Krs, 1968;
Krsová et al., 1989; Liu and Sternberg, 1993). Accurate recording of the paleomagnetic field would require rocks
that have not mechanically rotated since becoming magnetized (Jones et al., 1984; de Boer et al, 2001).
Acknowledgments
I
thank the National Park Service (Theodore Roosevelt National Park) for accommodations, and the NPS and the
US Forest Service for permissions to work on federal lands. Oscar Knudtson of the US Forest Service was a
knowledgeable guide to localities of recently burning coal seams. Caitlin Lippincott assisted with sample
measurements and Andy Sparks with field work and compilation of data. Franklin & Marshall College provided
various types of financial assistance.
Important Terms
diurnal variation
paleomagnetism
ferromagnetism
paramagnetic
isothermal remanent magnetization
pseudo-single domain
magnetic anomalies
rock magnetism
magnetic susceptibility
single domain
magnetometer
superparamagnetic
nanoteslas
thermal demagnetization
natural remanent magnetization
thermoremanent magnetization
paleointensity
References
Beechie, B., 2004, Coal outcrop fire suppression in the North Dakota Badlands; North Dakota Public Service
Commission, http://psc.nd.gov/ (accessed 10 June 2010).
Burger, H.R., Sheehan, A.F., Jones, C.H., 2006. Introduction to Applied Geophysics, second ed. W.W. Norton and
Co., New York, 554 p.
