Terminology for stratification and cross-stratification in sedimentary rocks

A terminology is suggested to aid the field geologist in describing the structures of stratified and cross-stratified rock units. Qualitative terms describing the character of rock layering are stratification, stratum, cross-stratification, cross-stratum, set, coset, and composite set. Quantitative terms applying to the thickness of stratification are very thick-bedded, thick-bedded, thin-bedded, very thin-bedded, laminated, and thinly laminated. Quantitative terms applying to the thickness of units into which the rock splits are massive, blocky, slabby, flaggy, shaly, platy, and papery.

A classification of cross-stratification is suggested, based primarily on whether the lower bounding surface of a set of cross-strata is one of erosion or nondeposition and, if erosional, whether it is plane or curved. Features of secondary importance in this classification are the shape of set of cross-strata, the attitude of the axis, the symmetry of the cross-strata with respect to the axis, the arching of the cross-strata, the dip of the cross-strata, and the length of individual cross-strata.