Calcareous conglomerate.
Credit: U.S. Geological Survery
A rock consisting of various-sized, round, water-worn stones cemented together, the binding material being generally of calcareous, siliceous, or ferruginous in character. Now and again the stones are held together by simple compression without any cement. Conglomerate is evidently gravel compacted into a more or less coherent mass. Like coarse gravel and shingle, some conglomerates are very tumultuous in appearance, and show no lines or planes of deposition. Generally, however, rocks of this kind exhibit roughly alternating layers of finer and coarser materials. The included stones may consist of any kind of rock or mineral, but the harder species, such as quartz-rock and quartz, are able to preponderate. Conglomerates are generally beach-deposits, either marine or lacustrine; sometimes they are of fluvial origin.
