由丹麦学者 N. Steno(1638-1686)于1669年一 次提出(Steno’s stratigraphic axioms)
Principle of Superposition In any sequence of undisturbed strata (rock layers), the oldest layer is on the bottom and the youngest is on the top. Principle of Original Horizontality Sediments settle from fluids under the influence of gravity, therefore the deposits are nearly horizontal or at very shallow inclines. Principle of Lateral Continuity A water-laid stratum, at the time it was formed, must continue laterally in all directions until it thins out as the result of nondeposition or until it abuts against the edge of the original basin of deposition.
3.2.1 Concepts of Stratigraphic subdivision and correlation
地层划分：根据 地层的特征和属 性（如岩性和化 石等）将地层组 织成相应的单位
Stratigraphic subdivision: The systematic organization of the Earth's rock bodies, as they are found in their original relationships, into units based on any of the properties or attributes that may be useful in stratigraphic work.
