structural geology, propagation mechanics and - Stanford School of ...

Although the Aztec sandstone experienced less than 1% total shortening as the result
of CB formation, the low-porosity, low-permeability band fabrics developed have been
shown capable of exerting profound fluid flow effects at scales of practical interest. The
analysis presented here of CBs as indicators of paleostress and tectonic structure in this
exhumed analog aquifer/reservoir also applies in reverse. That is, given knowledge of the
stress and material history of a subsurface sandstone, predictions regarding the possible
presence and geometry of CBs can be made.
2. Introduction
Compaction banding as a recognized mode of localized brittle failure in porous
sandstone has a brief history, having first been described and named by Mollema and
Antonellini (1996) based on their work in the Navajo sandstone of south central Utah.
Compaction bands (CBs) represent one kinematic end member of the suite of structures
known collectively as deformation bands, which includes shear and dilation bands (Du
Bernard et al., 2002; Borja and Aydin, 2004). Mollema and Antonellini (1996) described
CBs as long (meters), thin (centimeters) tabular zones of mechanical porosity loss formed
within the compressional quadrants of shear band style faults (Aydin, 1978), interpreting
them as “a structural analog for anti-mode I cracks in æolian sandstone...that
accommodate pure compaction,” following the conceptual anticrack model for pressure
solution surfaces of Fletcher and Pollard (1981).
The recognition of CBs, and their obvious potential to act as low-porosity, low-
permeability impediments to fluid flow in otherwise highly transmissive sandstones, has
excited an ongoing flurry of work both experimental (e.g. Olsson and Holcomb, 2000;
Klein et al., 2001; Vajdova and Wong, 2003; Haimson, 2003; Baud et al., 2004; Tembe et
al., 2006) and theoretical (e.g. Olsson, 1999; Issen and Rudnicki, 2000, 2001; Detournay
et al., 2003; Bésuelle and Rudnicki, 2004; Rudnicki, 2002, 2003, 2004; Katsman et al.,
2005; Rudnicki and Sternlof, 2005; Sternlof et al., 2005; Katsman and Aharonov, 2006)
all of it aimed at comprehending the mechanics of compaction localization in porous,
granular materials. To date, however, the only other field-based study published on CB
occurrence and geology also focused on an æolian Jurassic sandstone of the southwestern
U.S.—the Navajo-equivalent Aztec sandstone of southeastern Nevada (Sternlof et al.,
2005). That paper presents an anticrack-inclusion mechanical model for CBs that is based
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