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then compacted in the laboratory using the Hamano
device. The important advantage of using Hamano's
device is that the load could be applied very slowly
(over 8-10 hours) so that the slurry samples were not
over - pressured causing non - equilibrium conditions,
thus better mimicking natural burial compaction. In
all these experiments the break in slope compaction
behavior fi rst observed in Deamer & Kodama's (1990)
compaction experiments and then studied in detail by
Sun & Kodama (1992) was also observed. In addition,
inclination shallowing always occurred and the mag-
nitude of the shallowing was similar (Pigeon Point
Formation:
f
= 0.67; Ladd Formation:
f
= 0.65; Point
Loma Formation:
f
= 0.56; Nacimiento Formation:
f
= 0.74) which, for the intermediate inclinations for
these rocks, resulted in
c.
10 - 20 °
of
inclination
shallowing.
Tan
et al
. (2002) was the fi rst paper to examine the
effects of laboratory compaction on the inclination of
red bed analogues with natural hematite particles car-
rying the remanence of the sediments. Tauxe & Kent
(1984) conducted a pioneering study of inclination
shallowing in red bed material collected from the Siwa-
liks of Pakistan, re-deposited both in the laboratory
and in natural conditions along the fl oodplains of the
Soan River. Their re-deposition experiments showed
large amounts of syn-depositional inclination shallow-
ing with a fl attening factor of
f
= 0.4. Tan
et al
. (2002)
however re-deposited red bed material in the labora-
tory and then compacted it with the Hamano compac-
tion device to see the effects of post-depositional
compaction. The material they used was disaggregated
from the Eocene Suweiyi Formation of central Asia,
one of the units showing anomalously shallow inclina-
tions for this part of the world during the Late
Cretaceous - Early Tertiary.
To reconstitute these red beds, distilled water was
added to make a slurry for the compaction experi-
ments. One complication that occurred during the
work was that the slurry spontaneously segregated
into silt- and clay-sized parts. These two different slur-
ries were compacted in the laboratory as well as a 1 : 1
mixture of the two. The clay-sized slurry experienced
17 - 19 ° of inclination shallowing (
f
= 0.52) while
the silt-sized slurry showed little laboratory compac-
tion inclination shallowing (3° or
f
= 0.89). The 1 : 1
mixture of clay and silt material also saw small
amounts of shallowing (6° or
f
= 0.80). The break in
slope compaction behavior fi rst observed by Deamer
and Kodama was also observed, particularly for the
clay-sized slurry, reinforcing the notion that clay-rich
Fig. 4.6
Flattening factor
f
tan
I
f
/tan
I
0
for inclination
shallowing as a function of percent clay content. The
fl attening factor decreases and inclination shallowing
increases with increasing clay content. Clay contents as low
as 15% are observed to cause signifi cant inclination
shallowing.
=
All of these observations made in the early labora-
tory compaction shallowing experiments at Lehigh
could not have been made without the patient, careful
and painstaking work of Gwen Anson, Gay Deamer
and Wei Wei Sun.
LABORATORY EXPERIMENTS TO
CORRECT INCLINATION SHALLOWING
Subsequent laboratory compaction work with
magnetite-bearing sediments was all conducted as part
of inclination - shallowing anisotropy - based correc-
tions that will be covered in depth in the next chapter.
This work was all published in the mid-late 1990s.
Kodama & Davi (1995) corrected the inclination of the
Cretaceous Pigeon Point Formation marine sediments
from central California, Kodama (1997) tested the
anisotropy - based inclination - shallowing correction
with Paleocene continental sediments from New
Mexico and Tan & Kodama (1998) conducted an
inclination-shallowing correction of Cretaceous marine
sediments from southern California. In all these experi-
ments, the original sedimentary rock material was dis-
aggregated and reconstituted as a slurry which was
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