Diagenesis: Deformation Features
2015. "Diagenesis: Deformation Features", A Color Guide to the Petrography of Sandstones, Siltstones, Shales and Associated Rocks, Dana S. Ulmer-Scholle, Peter A. Scholle, Juergen Schieber, Robert J. Raine
Download citation file:
This chapter covers a range of structural features that can occur at thin-section scale in terrigenous rocks, including natural fractures, deformation bands, grain-scale strain features, stylolites and cone-in-cone structures. However, soft-sediment deformation features are not substantially covered here, because they are visibleatthin-sectionlevelprimarilyinveryfine-grained strata, and thus were previously illustrated in Chapter 8); likewise, compaction-related deformation features were largely covered in Chapter 10. The structures discussed in this chapter, especially fractures and deformation bands, play a major role in porosity-permeability relationships and hydrocarbon reservoir performance of many sandstones and mudstones. Although tectonic processes are commonly inferred to be the causes of brittle deformation structures, elevated pore-fluid pressures (and rapid or episodic loss of such overpressures) also have been shown to play a major role in formation of many natural fractures and veins (e.g., Cartwright, 1994; Miller, 1995; Conybeare and Shaw, 2000; Cosgrove, 2001; Cobbold et al., 2013). Natural overpressures can be generated in a variety of settings as a result of rapid burial of low-permeability strata, hydrocarbon generation, expulsion of water from evaporites and other processes (e.g., Burrus, 1998; Swarbrick and Osborne, 1998), and artificial generation of elevated fluid pressures is the basis of modern induced hydraulic fracing.