The first of four sections of the book is devoted to petrography, with an introductory overview of methodology by two of the editors. Methods appraised include thin-section microscopy (valuable, but requiring labour-intensive preparation), electron microscopy, x-ray diffraction analysis, study of light and heavy minerals and infrared absorption spectroscopy. A further three papers in that section provide examples of detailed studies: petrography of the Tertiary Boom Clay, northern Belgium; geochemistry of accessory minerals as a guide to provenance, as in the Carboniferous Stanley Formation of Arkansas; and Silurian shale fabric in New York State.

The second section is on petrophysical observations and comprises one well-illustrated paper on the permeability history of subsiding shales. Section three is the longest and contains eight papers covering diagenesis and geochemistry. A review paper entitled "Shale diagenesis: a currently muddied view" provides some history of research. Topics in other papers cover: potassium enrichment in shales ("a complex problem"); reconstructing Mid-Ordovician explosive volcanism from shale composition; potassic shale of the Central Appalachian Palaeozoic; diagenetic and detrital illite quantified; Sr/Nd geochemistry and mineralogy in the Shikoku Basin, Philippine Sea; rare-earth geochemistry of Cretaceous shale, Utah; and trace element remobilization in Ordovician black shale of Ontario and New York (remobilisation of rare earths appears to occur during late diagenesis).

The final section, on economic geology, contains a general review paper, by two of the editors, and a contribution on metal-rich black shale - formation, economic geology and environmental aspects (including some practical advice on sample collection). Shales are evidently of economic importance in many ways: hydrocarbon source rocks, repositories of metallic ore deposits such as Mount Isa and McArthur River; applications in ceramics, bricks and refractories; and long-term containment of hazardous waste.

AMF Alert 2 (4) 2000, page 39

published by the Australian Mineral Foundation, Glenside

The 31 papers in the 2 volumes are from a theme session in 1995 of the Geological Society of America. Volume I includes sections on stratigraphy and basin analysis, deposition of mudstone and shale, and paleontological obsess lions. Volume II contains petrography diagenesis/geochemistry, and economic geology. Each book has a subject index. There is great variation in the number of references in each paper, but overall there are a large number of citations to the literature. As one expects, a good case can be made for an equal number of used articles that are uncited.

Many of the shale specialists have authored or co-authored two articles. These include T. J. Algeo, J. Bloch, K M. Bohacs, K E. Goggin, J. T. Haynes, J. C. Hower, R. Hubbell, J. Jamimski, J. B. Maynard, W. G. Melson, T. O'Hearn, and W. Zimmerle. P. S. Sethi, a co-editor, contributed to three papers; the senior editor, J. Schieber, to a gargantuan five.

Shale is not studied to the extent sandstone and carbonate rock are because there is less economic interest in shale, it is difficult to study, and many geologists think a shale sequence is about as exciting as the third hour of a faculty meeting concerned with curriculum. We should devote more energy to shales than we do because they are by far the most abundant sedimentary rock; thus, they are the most common rocks at the earth's surface. The greatest amount of Phanerozoic history is held in fine-grained sedimentary rocks. Kevin Bohacs's wonderful quote from H. C. Sorby (1908) is apt: " - e accumulation of mud) is soon found to be so complex a question, and the results so dependent on so many variable conditions, that one might feel inclined to abandon the inquiry, were it not that so much of the history of our rocks appears to be written in this language."

In many sequent, Ends records short-lived, high-energy, depositional events, as Schieber and Zimmerle say. Shales may register long-term events and, when we can read them, common depositional conditions.

Space does not permit mentioning all of the fine work. Paul Potter, co-author with d. B. Maynard and Wayne Pryor of the useful volume Sedimentology of Shale, has examined shale-rich basins: "Why are some basins so rich in shale, others have but little, and in some it is virtual absent? . . . To me, search for a general model of shale does not need more data and more studies but rather only our attention." Another article of general interest is Bohacs's study of "Contrasting Expressions of Depositional Sequences in Mudrocks from Marine to Nonmarine Environs." The discussion of parts of the Green River (Paleocene-Eocene) Formation in the Wyoming Green River Basin is welcome because the formation is probably the most written about (and perhaps studied) fine-grained sequence in the world. Green River shales are significant hydras carbon source rocks in the Utah Uinta Basin, and the world's largest deposits of high-grade oil ~shale" (not really shale) occur in the Piceance Creek Basin of northwest Colorado, as Sethi and Schieber say in their paper on Economic Aspects of Shales and Clays: An Overview."

There is something here to please everyone who studies mudstone. Each article has something to offer. The authors know their way around finegrained sedimentary rocks.

M. Dane Picard, University of Utah, USA

AAGP Bulletin, December 1999, p. 2032