The distribution of values of dispersion of cross-stratification (measured as variance, at outcrop level) in Proterozoic rocks can be compared directly with patterns obtained from published descriptions of Phanerozoic rocks of more certain origin in order to augment environmental interpretations of the older sequences. Fluvial patterns show characteristic peaks below a variance of 4000; marine sequences show a broad distribution of values with characteristic peaks above 4000. Patterns obtained from aeolian deposits and (?) marine deposits in which unidirectional currents were important are difficult to distinguish from fluvial patterns. Hence, in Proterozoic arenite sequences, the observed distribution of variance values should be used only in conjunction with other environmental indicators.