Download Detrital Remanent Magnetization (DRM)

Magnetic field including all terms
Hulot et al., 2002
Magnetic minerals:
Ferromagnetism
Ternary diagram of the irontitanium oxide solid solution
magnetic minerals
Two most useful natural rock magnetizations
(NRM, Jr) for paleomagnetism
Detrital Remanent Magnetization (DRM)
• formed during or soon after deposition of sediments
• locked in by compaction and lithification to sedimentary rock
• relatively weak
Thermo-remanent Magnetization (TRM)
• formed in basic igneous rocks (e.g., basalt) upon cooling through
Curie temperature
• locked in upon further cooling
• very strong
thermo-remanent magnetization, TRM
Detrital remanent magnetization DRM
Paleomagnetic measurements
 Collect many suitable samples (e.g. basalt) with in situ
orientation determined
2001 Paleomag trip to Grand Canyon
We drilled the
Tapeats sandstone
from the Cambrian;
involved lots of
water to cool the
drill (me at top,
Dave Evans, Yale
below)
In August, 2001 I
was one of about 12
student slaves on a 2
week rafting trip
down the Grand
canyon to collect
paleomag samples.
Led by Joe
Kirschvink, Caltech
Because we were in a national
park, we had to patch the drill
holes once the samples were
removed. Here I am mixing
some concete with local rocks
Good result
Bad result
thermal demag (°C)
AC demag (mT)
Isolation from environmental and geomagnetic fields
cage
Mu metal encased room
corrections for structure
corrections for structure
Blocks rotated
during Neogene
Mojave extension
(Miocene)
Paleomagnetic declinations
Declination vrs age for the
western Transverse Block
Samples from this area
Closing the North Atlantic
Ordovician to Jurassic (500-200 Ma) “Apparent polar wander” (APW) paths for North
America and Europe
Europe rotated by 38 degrees about
rotation pole at 88.5N, 27.7E
Errors (a95 cones of confidence)