Experimental work on the effect of pre-existing anisotropy on fabric development in glaciers
Published:January 01, 2000
Christopher J. L. Wilson, 2000. "Experimental work on the effect of pre-existing anisotropy on fabric development in glaciers", Deformation of Glacial Materials, Alex J. Maltman, Bryn Hubbard, Michael J. Hambrey
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Localization of deformation in ice is known to be important at all scales in deforming glaciers. However, relatively little is known of the significance of shear localization and the influence of fabric development in anisotropic ice at microscopic scales (<mm–cm). In this experimental study, the effect of initial c-axis preferred orientation and the inclination of the primary layering in anisotropic ice masses, during both plane strain-compression and combined simple shear-compression, have been examined. A series of creep tests in the temperature range of –5 to –1°C over a range of shortening strains varying from 10 to 40% and compressive stresses ranging from 0 to 0.7 MPa have been undertaken. Significant variations in the strain rate and microstructural development have been observed in the plane strain-compression experiments that reflects the varying orientations of the anisotropy and its relationship to easy-glide directions in the ice mass. In the unconfined combined compression and shear experiments minimum shear stress rates vary between the variously oriented anisotropic ice masses and deviate from the normal power flow law for isotropic ice. Where annealing occurs, such ice masses preserve the pre-existing c-axis fabric and hence may reflect a contribution from both the recrystallized and inherited ice components.
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Deformation of Glacial Materials
The flow of glacier ice can produce structures that are striking and beautiful. Associated sediments, too, can develop spectacular deformation structures, and examples are remarkbly well preserved in Quaternary deposits. Although such features have long been recognized, they are now the subject of new attention from glaciologists and glacial geologists.
This collection of papers addresses how the methods for unravelling deformation structures evolved in recent years by structural geologists can be used for glacial materials, and the opportunities offered to structural geologists by glacial materials for studying deformation in rocks.