Mixed Clastic–Carbonate Cycles and Sequences: Quaternary of Egypt and Carboniferous of England

In the geological record one tends to think of formations composed of either limestones or sandstones, but rarely both. In fact, there are many cases of interbedded clastics and carbonates in repeated cyclic arrangements. Such units occur on the small-scale (metre-thick cycles or parasequences, 4/5 order), and on the larger-scale (10’s metre-thick, 4 order high-frequency sequences and 100’s metre-thick, 3 order sequences). Mixed lithologies, namely sandy limestones and calcarenaceous sandstones are relatively rare rocks, or at least they are rarely described and classified properly. Terrigenous input is dominantly a function of clastic availability and relative sea-level change, with the rate of change of major significance (see MOUNT, 1984 Mixed Clastic–Carbonate Cycles and Sequences: Quaternary of Egypt and Carboniferous of England