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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 56 (1972)

Issue: 11. (November)

First Page: 2150

Last Page: 2159

Title: Dielectric Anisotropy and Grain Orientation

Author(s): A. M. Winkelmolen (2)


When grain-orientation studies are used to infer sedimentologic trends such as sand-body elongation, one must be sure that the observed orientation originated during the genesis of the sand. Postdepositional changes of the grain-orientation pattern easily can occur. Symmetry considerations can suggest whether an observed pattern is depositional or secondary. Integral bulk techniques, like the measurement of dielectric anisotropy (DA) on cylindrical plugs, inevitably produce a sinusoidal signal, because the symmetry of the measuring principle is superimposed on the symmetry properties of the sample fabric.

Furthermore, the DA and other analogous bulk methods do not measure grain orientation exclusively. Other phenomena, such as bedding and crystal-lattice orientation, may be dominant. By changing the setup of these bulk methods, improvements can be made. For an optimal evaluation of the fabric properties, however, a detailed picture of the grain long-axis distribution pattern is necessary, together with knowledge of the relation between grain orientation and other directional features, especially the foresetting. Best results in grain-orientation work can be obtained only by methods based on geometric principles that exclusively measure grain long-axis orientation.

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