A note on sand dyke orientations

The techniques of the statistics of directional data are applied to the orientations of sand dykes and bedding in strata unaffected by significant penetrative tectonic strain or compaction. From the records of the orientations of both bedding and sand dykes in 578 individual cases it is shown that the mean bedding-dyke dihedral angle for each group of dykes recorded in the literature ranged from 87.7 to 89.6°. The hypothesis is accepted that these dykes tended to form perpendicular to bedding. This has beneficial implications for their use as strain markers in compaction studies and in tectonic strain analysis.