ABSTRACT

Cross-stratification is a well-known structure in many detrital limestones. Several examples of very small scale cross-lamination in fine-grained limestones are described in the present paper, and these are cited as evidence of detrital origin. Cross-lamination in a limestone implies mechanical deposition of current transported particles and indicates that the limestone has not been precipitated in place.

Cross-lamination occurs on various scales in detrital limestones. In very fine-grained limestones, cross-laminae occur in "sets" of small dimensions, ranging in thickness from less than 1/25 of an inch to more than one inch, and in length from 1 to 2 inches to 6 or 8 inches. Small scale cross-laminae usually have angles of inclination from the horizontal of 20 degrees or less. Frequently, small-scale ripple marks occur with cross-lamination. Cross-stratification is also common in coarse, mechanically-deposited limestones such as calcarenites and limestone conglomerates. The maximum angle of inclination of cross-strata is greater in coarse grained limestones than in fine grained limestones. In calcarenites and in limestone conglomerates, the angles of inclination may range as high as 3 or 40 degrees from the horizontal.

Examples of small scale cross-laminations and of cross-bedding occurring in the upper portion of the Arbuckle Limestone of south-central Oklahoma are shown by negative peel prints and photographs in the present paper.