ABSTRACT
Petrographic study has been carried out on slickenside thin
sections,
to find out reliable microstructures for determining the
slip-sense of
faults, and to classify slickensides morphologically. Thin
sections are
made cut parallel to the striation and perpendicular to the slip
plane.
Many useful slip-sense indicators are found in thin section even
though
such indicators may be absent in hand specimens. They are (1)
off-set or
bending of once-continuous bodies such as veins, layers, grains or
twin
lamellae, (2) crystal fibers growing nearly parallel to the slip
direction,
(3) extensional fractures aligned oblique to the slip plane, (4)
S-C geometries
in ductile materials, and (5) Riedel- and P- shear fractures
associated
with the main slip surface.
Two distinct layers may exist adjacent to the slickenside surface.
One is termed coating: a discrete layer of material immediately
under the
slip surface. The other is termed the deformed host layer which is
a zone
of deformation in the host rock developed parallel to the
slickenside.
Slickensides are classified into four morphological types
depending on
the presence or absence of coating and deformed host layers. They
are type
A (deformed host layer only), type B (coating and deformed host
layer),
type C (no coating and no deformed host layer), and type D
(coating only).
This morphological classification can be a first step toward
further
genetic interpretation of slickensides, which could eventually be
used
to infer conditions of faulting. Possible development paths of
each slickenside
type indicate that present slickenside morphology can be
influenced by
rock type, slip-rate and depth of faulting during slip and by
weathering
and precipitation of veins along the pre-existing slip surface
after slip.
Although this classification is not yet fully satisfactory, it can
perhaps
be extended and improved by further systematic slickenside
studies.
Lee, Y-J., 1991. Slickenside petrography: slip-sense indicators
and
classification.
Unpublished MSc. thesis, State University of New York at Albany.
100
pp., +x
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 40 Z899 1991 L44
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text) - 13.2MB pdf file
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