Book review
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Book review Garry Karner, Brian Taylor, Neal Driscoll, and David Kohlstedt (eds), Rheology and Deformation of the Lithosphere at Continental Margins, Columbia University Press, New York, 2004. I had considerable difficulties completing my review of this volume owing to its popularity among research colleagues, graduate, and advanced undergraduates. No sooner would I wade through a meaty, well-illustrated chapter than it would disappear to a postgrad office, or the copier. It is a long overdue review of progress in plate boundary processes, which are critically dependent upon lithospheric rheology. And, in keeping with the style of the first editor, the various chapters are brimming with explicit and implicit controversy. The book comprises 11 chapters on what at first appear to be an eclectic mix of topics. But, as clearly explained in the witty preface, these topics and authors were chosen to present paradoxes or controversy that span extensional, compressional, and strike-slip plate boundary settings. The papers respond to the questions ‘Where are we now, and what should we do next?’, a stimulating mix of review and personal statement, theory and observation. All chapters extract constraints on lithospheric rheology, and relate rheology to process. All but one chapter include a balanced bibliography. Chapters 1, 3, and 4 focus on extensional deformation of continental lithosphere. In Chapter 1, Roger Buck presents his three paradoxes, which are in part fundamental to our understanding of the rheology of the continental plates: (a) Are plate driving forces large enough to rift strong continental lithosphere? (b) Why do some margins show excess subsidence? (c) Why are some margins amagmatic? Buck provides an elegant explanation with his conceptual ‘magma-assisted’ rifting model. He also presents provocative new ideas, sensibly adding strain accommodation by melt intrusion to the already complex problem of extension of rheologically layered lithosphere. Chapter 3, by Gary Axen, tackles the paradox of active low-angle normal
faults and Byerlee friction laws, which are also considered by Chris Scholz and Thomas Hanks in Chapter 9. Axen reconciles observations of low-angle detachment fault systems with rock mechanics and geophysical data, but also concludes that considerably more needs to be learned regarding the strength of fault zones, nicely introducing Chapters 8 and 9. In Chapter 4, Mark Davis and Nick Kusznir present an alternative explanation for the ‘Subsidence paradox’ of Buck. These authors take a more traditional approach of pure versus simple-shear in their review. Davis and Kusznir provide observations and theory for a time dependent, depth-dependent stretching model whereby differential stretching at different depths increases with stretching factor. Chapters 2, 5, and 6 extract information on rheology from seismology, and make links to the longer-term deformation derived from geodesy and isostasy. Quoting from the editors, James Jackson ‘…introduces a contentious idea, suggesting that the strength of the continen
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