2015. "Diagenesis: Compaction", 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:
Compaction is one of the major processes by which sediments lose porosity and begin the transformation to sedimentary rocks. Compaction is driven mainly by overburden loading and involves changes in the packing density of constituent grains. This is accomplished initially through grain reorientation and repacking accompanied by water expulsion from porous sediments. With additional overburden loading, fracturing and cleavage of brittle grains and plastic deformation of ductile grains contribute to increased packing density and concomitant loss of pore space. Further reduction of intergranular pore space, beyond that produced by “mechanical compaction”, results from pressure-solution processes, sometimes termed “chemical compaction”. Chemical compaction includes selective dissolution and interpenetration at grain-to-grain contacts, as well as broader dissolution along solution seams and stylolites. Although more common in carbonate rocks, chemical compaction features are widespread in clastic terrigenous deposits as well (e.g., Heald, 1955; Walderhaug and Bjørkum, 2003).
Figures & Tables
AAPG Memoir 109 is designed as a practical guide for students and professionals to learn the fundamentals of microscopic examination of sandstones, mudrocks, and associated rocks. With more than 1100 color illustrations, it covers the identification of grains, textures, and structures of clastic terrigenous rocks as well as their diagenetic alteration (compaction, cementation, dissolution, and replacement) and porosity reduction or enhancement. It also provides classification diagrams for formal description of those rocks and their porosity. Although the majority of the outcrop and subsurface examples come from the United States (35 states and Puerto Rico), there are representative photographs from 32 other countries, including many from the offshore areas. The foldout birefringence chart and an included DVD with Powerpoint files of all of the petrographic images provide additional aids for instructors and students.