Sand Smear Along
Sorkhabi, Rasoul1 (1)
Energy and Geosciences Institute,
“Shale smear” in normal faults has been
recognized as an effective fault sealing process and algorithms using this
phenomenon are widely and sometimes successfully used for fault prospect
analyses in sand-mud sequences. Several approaches have been suggested to
explain the shale smear. One approach suggests that undeformed
clastic sediments with a clay content of over 40
percent essentially deform by smear on fault planes. A second approach
classifies shale smears into shale on sand abrasion smears, brittle shear
smears, and gravitational injection smears. Fault-related shale injection is
thought to be due to a mechanical contrast between ductile mudstone and
relatively hard sandstone layers. This study shows that (1) rock smear is a
more general phenomenon in sedimentary basins and is necessarily not restricted
to shale, and thus, given an appropriate rheological
setting, sand can also create fault smear; and that (2) rock smear is not
limited to normal faults but may also develop in reverse fault zones. Evidence
for these observations comes from the late Miocene Nishizaki
Formation outcropped along the coast on
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California