- Email: [email protected]
The geological deformation of sediments
TECTONOPHYSICS ELSEVIER
Tectonophysics 263 (1996) 347-348
Book Review A. Maltman (Editor), 1994. The Geological Deformation ( f Sediments. Chapman and Hall, London, 362 pp. Rarely do I pick up a technical book and find myself hooked as if breezing through one of Tom Clancy's latest spy adventures. Based on the speed with which they captured my attention, Alex Maltman and his fellow experts on the world of soft sediment deformation are to be congratulated for their book, The Geological De~rmation of Sediments (GDS). It will be a treat for all who care to check it out. Although each chapter was uniformly informative and well written, Maltman and company had my attention for reasons beyond excellent workmanship. First, as a structural geologist I am on the lookout for new material that applies immediately to my field experience. My field area, the Devonian Catskill Delta of the Appalachian Mountains, is loaded with penecontemporaneous structures of the type described in John Collinson's chapter in GDS. Second, several chapters in GDS appealed directly to my interest in both state of stress in sedimentary basins and the effect of pore pressure on joint propagation. For more than a decade Dan Karig has warmed (not warned) me up to fact that stress in sedimentary basins evolves during burial from uniaxial consolidation rather than from elastic strain. I had previously made oblique reference to an elastic model in papers. In fact, on reading Chapter 6 of GDS, one will find that Dan is still on my case for this faux pas. GDS contains chapters on a wide range of subjects pertaining to soft-sediment deformation. In addition to Alex Maltman's introduction and overview, Mervyn Jones contributes a chapter on the mechani0040-1951/96/$15.00 Published by Elsevier Science B.V. SSDI 0 0 4 0 - 195 I ( 9 5 ) 0 0 2 0 4 - 9
cal principles of sediment deformation. The mechanics of particulate media draws heavily on the soils literature where degree of consolidation and critical state theory are important theoretical considerations. Tavi Murray presents a comprehensive look at deformation structures in glacial sediments where the effects of subglacial shear are imprinted. John Collinson compiles a marvelous set of photographs illustrating various types of penecontemporaneous structures found in fluvial and marine sediments. Even cross bedding of eolian sandstone can become contorted due to loss of strength below an active water table. Ole Martinsen deals with the structures accompanying mass wasting including falls, flows, slumps, slides and downhill creep. Dan Karig and Julie Morgan review their laboratory data on stress paths during burial and uplift in sedimentary basins. Here we learn that the ratio of horizontal stress to vertical stress ( K o) during burial is a larger fraction of unity than would be the case for uniaxial elastic strain. These lessons are then applied to the far more complex question of stress path in accretionary prisms. Kevin Brown reviews the role of fluids in deforming sediments while Tim Byrne relates his experience with the deformation, dewatering and diagenesis of selected m~lange zones. GDS concludes with a chapter by Alex Maltman on deformation structures on the microscopic and mesoscopic scale that are preserved in sedimentary rocks. Like any book of this size GDS contains thoughts and definitions with which one may quibble. For example, GDS uses pressure and stress interchangeably whereas I prefer to restrict the use of pressure to materials without shear strength (i.e., pore fluids) and stress to materials with a shear strength (i.e., rocks). Hence, I favor calling K o, the coefficient of
348
B o o k rez i e w
earth stress (not pressure) at rest. The soils literature commonly but mistakenly uses the term deviatoric stress in place of differential stress (or stress difference as Mervyn Paterson prefers). Some of us have pointed out that, unlike differential stress, deviatoric stress has a different definition that is not easily expressed as one term. In another place, GDS discusses mechanisms for joint propagation in sediments by drawing upon G r a m b e r g ' s model for joint propagation at rounded or elliptical crack tips. Most fracture mechanics literature points out that tips of cracks and joints are sharp, a condition for which G r a m b e r g ' s model is inappropriate. Even if the stress
concentration at crack tips leads to a plastic zone or crack-tip process zone, G r a m b e r g ' s model still does not apply. In summary, GDS contains material that will delight a cross section of Earth scientists from those interested in glacial geomorphology to those interested in the tectonics of subduction zones. GDS is a wonderful book and all involved in the project deserve a vote of thanks from the geoscience community. T. Engelder (University Park, PA)
Tectonophysics 263 (1996) 347-348
Book Review A. Maltman (Editor), 1994. The Geological Deformation ( f Sediments. Chapman and Hall, London, 362 pp. Rarely do I pick up a technical book and find myself hooked as if breezing through one of Tom Clancy's latest spy adventures. Based on the speed with which they captured my attention, Alex Maltman and his fellow experts on the world of soft sediment deformation are to be congratulated for their book, The Geological De~rmation of Sediments (GDS). It will be a treat for all who care to check it out. Although each chapter was uniformly informative and well written, Maltman and company had my attention for reasons beyond excellent workmanship. First, as a structural geologist I am on the lookout for new material that applies immediately to my field experience. My field area, the Devonian Catskill Delta of the Appalachian Mountains, is loaded with penecontemporaneous structures of the type described in John Collinson's chapter in GDS. Second, several chapters in GDS appealed directly to my interest in both state of stress in sedimentary basins and the effect of pore pressure on joint propagation. For more than a decade Dan Karig has warmed (not warned) me up to fact that stress in sedimentary basins evolves during burial from uniaxial consolidation rather than from elastic strain. I had previously made oblique reference to an elastic model in papers. In fact, on reading Chapter 6 of GDS, one will find that Dan is still on my case for this faux pas. GDS contains chapters on a wide range of subjects pertaining to soft-sediment deformation. In addition to Alex Maltman's introduction and overview, Mervyn Jones contributes a chapter on the mechani0040-1951/96/$15.00 Published by Elsevier Science B.V. SSDI 0 0 4 0 - 195 I ( 9 5 ) 0 0 2 0 4 - 9
cal principles of sediment deformation. The mechanics of particulate media draws heavily on the soils literature where degree of consolidation and critical state theory are important theoretical considerations. Tavi Murray presents a comprehensive look at deformation structures in glacial sediments where the effects of subglacial shear are imprinted. John Collinson compiles a marvelous set of photographs illustrating various types of penecontemporaneous structures found in fluvial and marine sediments. Even cross bedding of eolian sandstone can become contorted due to loss of strength below an active water table. Ole Martinsen deals with the structures accompanying mass wasting including falls, flows, slumps, slides and downhill creep. Dan Karig and Julie Morgan review their laboratory data on stress paths during burial and uplift in sedimentary basins. Here we learn that the ratio of horizontal stress to vertical stress ( K o) during burial is a larger fraction of unity than would be the case for uniaxial elastic strain. These lessons are then applied to the far more complex question of stress path in accretionary prisms. Kevin Brown reviews the role of fluids in deforming sediments while Tim Byrne relates his experience with the deformation, dewatering and diagenesis of selected m~lange zones. GDS concludes with a chapter by Alex Maltman on deformation structures on the microscopic and mesoscopic scale that are preserved in sedimentary rocks. Like any book of this size GDS contains thoughts and definitions with which one may quibble. For example, GDS uses pressure and stress interchangeably whereas I prefer to restrict the use of pressure to materials without shear strength (i.e., pore fluids) and stress to materials with a shear strength (i.e., rocks). Hence, I favor calling K o, the coefficient of
348
B o o k rez i e w
earth stress (not pressure) at rest. The soils literature commonly but mistakenly uses the term deviatoric stress in place of differential stress (or stress difference as Mervyn Paterson prefers). Some of us have pointed out that, unlike differential stress, deviatoric stress has a different definition that is not easily expressed as one term. In another place, GDS discusses mechanisms for joint propagation in sediments by drawing upon G r a m b e r g ' s model for joint propagation at rounded or elliptical crack tips. Most fracture mechanics literature points out that tips of cracks and joints are sharp, a condition for which G r a m b e r g ' s model is inappropriate. Even if the stress
concentration at crack tips leads to a plastic zone or crack-tip process zone, G r a m b e r g ' s model still does not apply. In summary, GDS contains material that will delight a cross section of Earth scientists from those interested in glacial geomorphology to those interested in the tectonics of subduction zones. GDS is a wonderful book and all involved in the project deserve a vote of thanks from the geoscience community. T. Engelder (University Park, PA)