Copyright by Nysha Chaderton 2009 - The University of Texas at ...

They are common in accretionary prism settings (Fossen et al., 2007). Deformation
bands were observed in 2 of the 10 samples point counted.
There is a reduction in porosity and permeability along deformation bands.
However there is thought to be an initial dilation that may aid in fluid flow and lead to
preferential cementation along these linear features (Ngwenya et al., 2000; Olgivie and
Glover, 2001; Fossen et al., 2007). Fractured quartz grains provide clean sites for
nucleation of quartz cements that are so abundant in sand (Walderhaug, 1996, Fossen and
Bale, 2007).
Although it is often thought that deformation band zones are baffles to fluid flow,
Fossen and Bale (2007) showed that the impact of deformation bands on reservoir
performance may be small or negligible.
Within the Scotland Formation samples, no quartz cementation was observed
within the deformation bands. This observation further supports the idea that the
Scotland Formation did not experience temperatures greater than 60˚C. In addition the
observations that cataclastic deformation bands develop at depths of 2.5 km or less and
even in sediments buried as shallowly as 50 m also support the concept that the Scotland
Formation was never buried very deeply.
Based on the calculations of the IGV of the samples which ranged from a
minimum of 27.5% to a maximum of 42 % the rocks of the Scotland Formation appear to
have been buried less than 2500 m and possibly only about 1500 m.
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