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

The initial intergranular volume is assumed to be 40-45% (Beard and Weyl,1973;
Pryor,1973; Atkins and McBride, 1992; Paxton et al., 2002). The amount of compaction
that the rock has undergone can be estimated based on the difference between the IGV
and the assumed initial intergranular volume of 40-45%. If cement and depositional
matrix are subtracted, the intergranular volume (IGV) is the maximum potential
intergranular porosity of the rock (Paxton et al., 2002).
Paxton’s IGV curve shows that mechanical compaction in the upper 1500 m of
burial corresponds to IGV values of 28-42%. From 1500-2500 m of burial, compaction
values range from 26 to 30% IGV and below 2500 m, sandstones reach maximum
mechanical compaction that corresponds to an IGV of 26% (Paxton et al., 2002).
FRAMEWORK GRAINS
Quartz
The quartz grains in the samples studied are predominantly monocrystalline with
less common polycrystalline quartz. These samples are dominated by common quartz. A
few quartz grains do have sutured boundaries and exhibit undulose extinction. Some
quartz grains are highly fractured (Figure 3.1).
Previous workers have documented quartz cement in the form of overgrowths.
Examination of the samples collected in this study shows that many of the overgrowths
in the samples are abraded and there are many grains with distinctive dust rims that allow
the overgrowths to be readily identified (Figure 3.2). This evidence suggests that the
quartz in these samples is of recycled origin and not part of the cementation history of
these rocks.
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