3. 2.1 Concepts of Stratigraphic subdivision and correlation 地层划分:根据地 DEVONIAN 层的特征和属性 tOid Red Sandstone) (如岩性、化石和 不整合面等)将地 ORDOVICIAN CAMBRIAN 层组织成相应的单 位 FIGURE 1-19 Generalized geologic cross-section for the Silurian-type region Unconformities separate the Ordovician from the Cambrian and Silurian systems. Silurian Stratigraphic subdivision: strata are inclined toward the east, with more resistant rocks forming escarpments that face toward the west The systematic organization of the earth's rock bodies, as 找异 they are found in their original relationships, into units based on any of the properties or attributes that +—1 may be useful in stratigraphic work. 图3—7地层剖面划分示意图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、化石和 不整合面等）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. 找异