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Introduction to carbonate petrology with discussions of classifications, facies, sequences, hydrocabon plays, photomicrographs, and exercises related to thin sections of carbonate rocks, etc.
This page leads into portions of a course on Carbonate Petrology. It provides access to photomicrographs and a series of exercises related to over 240 different thin sections of carbonate rocks. Some 1,700 images were captured, and as a result some thin sections have over ten images associated with them. The intent of this site is to provide students and professionals studying carbonates in thin section with an "identikit" of carbonate petrographic examples and exercises related to these, which can be used as a reference set to guide them through the examination of their own samples. Our hope is that you can access the site with your trusty microscope beside you and make direct comparisons between your samples and the ones we have provided. The site is not intended to replace texts like Scholle (1978) or Majewske (1969) but supplement these important texts.

The thin sections come from USC's extensive collection of carbonate thin sections largely assembled and collected by Christopher Kendall from Holocene and Ancient carbonates from all over the world. They are tied to a series of exercises written by Christopher G. St. C. Kendall which is based on the text of the carbonate petrography exercises that were developed by Robert L. Folk of the University of Texas at Austin.

While most carbonate grains are easy to recognize in hand specimen when seen in thin section they can be difficult to identify. The problem is, as Majewski(1969) remarked, that a "variety of shapes are produced by random cuts through a single geometric pattern, and shapes can be duplicated in such cuts by different designs; also, characteristic features may be obscured and others may become apparent" when the grains are exposed in a specific plane. Never the less the carbonate grains of this collection are separated from one another on the basis of their shape, size and internal structure.

Carbonate grains can be separated from one another on the basis of their shape, size and internal structure. Because the grains commonly collect near their site of origin, they can be used, in conjunction with other rock characteristics including vertical and lateral facies relationship and sedimentary structures, to determine the depositional of the rocks they occur in. Information about grain types and the manner in which they occur in rocks can be communicated by means of limestone classifications.

The interpretation of the depositional setting of carbonates is based on grain types, grain packing or fabric, sedimentary structures, and early diagenetic changes. The identification of grain types is commonly used in subsurface studies of depositional setting because, unlike the particles in siliciclastic rocks, the grains making up carbonates generally formed within the basin of deposition. This oversimplification or rule of thumb doesn't always apply. For example, ooid sands, which characteristically form on highly-agitated shoals, may also accumulate on beaches, islands, sand flats, deltas and even turbidite fans. Thus, while most carbonate geologists will use grain types to make an interpretation of depositional setting they should further test their hypothesis using the other criteria listed above.

Carbonate sedimentary particles may be subdivided into micrite (lime mud) and sand-sized grains. The grains can be separated on the basis of their shape and internal structure and can be subdivided into two major groups: skeletal and non-skeletal.

Useful Carbonate References

Most sedimentological texts will help you gain an understanding of carbonates, their depositional systems, facies and diagenesis. Listed below are a few:

Sam Boggs, 2006, Principles of Sedimentology and Stratigraphy, 4th ed., Pearson-Prentice Hall, 662 p.

Don Prothero & Fred Schwab, 2003, Sedimentary Rocks & Stratigraphy, W.H. Freeman & Co. 600 p.

James Lee Wilson, 1975, Carbonate facies in geologic history, Berlin ; New York : Springer-Verlag, 471 p.

R.G. Walker & N.P. James (eds), 1992, Facies Models, Response to Sea Level Change : the Geological Assoc. of Canada, 454 p.

Bathurst, R. C. G., 1976, Carbonate Sediments and their Diagenesis (Second Edition): Developments in Sedimentology, Elsevier, 658 p.

Bricker, O.P. 1971. Carbonate Cements. John Hopkins Press, Baltimore, 376 p.

Carozzi, A. V., 1989. Carbonate Rock Depositional Models: A Microfacies Approach, Prentice Hall, Englewood Cliffs, NJ, 604 p.

Cayeux, L. 1935. Les Roches Sedimentares de France. Roches Carbonatees Masson, Paris, 463 p.

Flugel, E., 1982, Microfacies Analysis of Limestones, Springer-Verlag, 633 p.

James, N.P., 1984, Shallowing-upward sequences in carbonates, in Walker, R.G., ed., Facies Models: Geological Association of Canada, Geoscience Canada, Reprint Series 1, p. 213–228.

Majewske, O.P. 1969. Recognition of Invertebrate Fossil Fragments in Rocks and Thin Sections. Brill, Leiden, 101 p.

Milliman, J. D., 1974, Marine Carbonates: Recent Sedimentary Carbonates Part 1: Springer-Verlag, 375 p.

Rao, C. P., 1996, Modern Carbonates - tropical, temperate, polar: University of Tasmania, 206 p.

Scholle, P. A., D. G. Bebout, and C. H. Moore (eds.), 1983, Carbonate Depositional Environments: AAPG Memoir 33, 708 p.

Scholle, P. A. and Ulmer-Scholle, D. S, 2003, A Color Guide to the Petrography of Carbonate Rocks: AAPG Memoir 77, 474 p

Scoffin, T. P., 1987, An introduction to Carbonate Sediments and Rocks: Blackie, 274 p.

Tucker, M. E., and V. P. Wright, 1990, Carbonate Sedimentology: Blackwell, 482 p.

Reading, H. G. (ed) , 1996, Sedimentary Environments: Processes, Facies and Stratigraphy. Third edition. Blackwell, Oxford, p688.

Wray, J.L. 1977. Calcareous Algae (Developments in Paleontology and Stratigraphy No. 4). Elsevier, New York, 185 p.

Other useful references can be found in the Carbonate Reference Page on this site.