Abstract

Statistical grain orientation studies of two unmetamorphosed ripple-marked sandstones, a ripple-marked quartzite, and four pseudo ripple marks show that a distinction between ripple marks and pseudo ripple marks can be made from fabric characteristics even when field data are equivocal. Some of these pseudo ripple marks had been previously interpreted as ripple marks.

Quartz diagrams were prepared for all the rocks, and mica diagrams for those that contained mica. Without exception, the axes of the pseudo ripple marks are important fabric directions, both for mica and quartz. The ripple-mark axes are also principal fabric directions for mica, but there are important and easily recognizable differences between the arrangement in the ripple marks and pseudo ripple marks. Quartz orientation in the ripple-marked sandstones may or may not be significant, but it is radically different from that found in the pseudo ripple marks.

The origin of each pseudo ripple mark is discussed briefly.

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