Original Horizontality (Nicolaus Steno, 1638-1687). The sediments that form sedimentary rocks have been transported to the depositional basins mainly by the action of water, and to a lesser extent, wind. Once in the depositional basin, shallow water currents and gravity have a leveling affect on the sediments. Because of this, the vast majority of sedimentary rocks were originally formed as horizontal formations. If sedimentary beds are inclined at severe angles, and they often are, some type of force must have deformed them from their originally horizontal position after they had been lithified into solid rock.