Skip to Main Content
Book Chapter

Diagenesis

By
Published:
January 01, 2015

Abstract

The term “diagenesis” refers to essentially everything that happens to sediments and rocks after their deposition but prior to metamorphism. There are a variety of diagenetic processes, biological, chemical and physical, that ultimately convert sediments into sedimentary rocks. The earliest of those events are covered in this chapter on near-surface diagenesis; subsequent chapters cover processes and products that occur primarily during later stages of diagenesis (mainly mesogenesis). Those include mechanical and chemical compaction, cementation, dissolution, replacement and structural deformation. All these processes can profoundly affect the porosity, permeability and hydrocarbon reservoir potential of clastic terrigenous deposits, and most of them are a function of initial sediment composition and the changes in pressure, temperature and water chemistry that accompany progressive burial. Less explicitly covered, but potentially no less important, is diagenesis that can occur during one or more episodes of local or regional uplift and consequent exposure (telogenesis). These events also introduce changes in the pressure/ temperature/water chemistry regime of rocks, and thus can cause major diagenetic changes, especially grain dissolution and cementation. In an attempt to address the impacts of the various diagenetic events that rocks may experience, this book includes both a section on the recognition of porosity types as well as one on paragenesis (i.e., the placement of diagenetic events into a temporal sequence related to the burial/uplift history of rocks). Burial diagenesis is critically important in controlling the porosity of clastic terrigenous rocks and is, in the main, porosity destructive—that is, almost all rocks lose porosity with increased burial depth. Nonetheless, several factors can retard or inhibit porosity loss, including early grain-coating cements, that block later overgrowth cementation, regional overpressuring of basins that reduce effective overburden stresses and, under some circumstances, hydrocarbon entry that can reduce rock-water interactions. In addition, the processes of dissolution and fracturing may, under the right circumstance, lead to actual increases in subsurface porosity. So the discussion of porosity destruction, preservation and creation pervades all chapters in the diagenesis section, and emphasis is placed on recognition of key features associated with anomalous porosity retention or creation.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

AAPG Memoir

A Color Guide to the Petrography of Sandstones, Siltstones, Shales and Associated Rocks

Dana S. Ulmer-Scholle
Dana S. Ulmer-Scholle
Search for other works by this author on:
Peter A. Scholle
Peter A. Scholle
Search for other works by this author on:
Juergen Schieber
Juergen Schieber
Search for other works by this author on:
Robert J. Raine
Robert J. Raine
Search for other works by this author on:
American Association of Petroleum Geologists
Volume
109
ISBN electronic:
9781629812731
Publication date:
January 01, 2015

GeoRef

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now