Internal Structure of
Deformation Bands of Cambrian-aged Hickory Sandstone (central Texas)
Milliken, K. L. and Reed, R. M. (2002)
GCAGS, 52, 725-736
Deformation
bands in porous sandstones significantly effect the permeability and
lithification in sandstones - Why?
SEM-CL establishes the important role
of brittle processes and quartz cementation in deformation bands
- Hickory sandstone on Precambrian
basement of Llano Uplift - burial estimates about 1 km
- Deformation bands subparallel to
local faults
Petrographic features of deformation
bands:
- reduced pore and particle size
- possible intra- and transgranular
fracturing
- quartz cementation in undeformed
portion
SEM-CL features of deformation bands:
- dominance of brittle deformation is
obvious
- intragranular fracturing is minor in
the band interior with rounding and comminuted matrix
- extensive quartz cementation former
pore spaces
- significant grain size reduction and
heterogeneous deformation
- linear arrays of related grains on
breakage
- small particle fill in fracture
implies comminution of grains prior to cementing
Sequence of deformation and cementation
events:
- multiple brittle deformation and
cementation
- starts with grain crushing (probably
of point grain contacts)
- grain gliding with grain size
reduction
- there is likely initiation of
deformation band with single grains and proceeding outward
- the central zone of the band is the
end-product with rounded grains in crushed matrix
