第十二章 地层单位和地层系统资料.ppt

第十三章 地层单位和地层系统;1 岩石地层单位（Lithostratigraphic Unit）定义：由岩性、岩相或变质程度均一的岩层构成的地层体，即以岩性岩相为主要依据而划分的地层单位分级：群、组、段、层;岩石地层单位-组 定义：组是基本的岩石地层单位,具有相对一致的岩性、岩相和变质程度，且具有一定结构的地层体。建组条件：1)岩性相对一致（均一、夹层、互层或特别复杂）;2)内部结构一致（内部不分段的组为一种结构类型，内部分段的组可有多种结构类型）;3)顶底界线明显（不整合或明显的整合）;4)一定和厚度和分布范围（一般要求能在区域地质图（1/5-1/20万）上表达）。;岩石地层单位-lithostratigraphic units 群-Group：通常是组的联合。联合原则：岩性的相近；成因的相关；结构类型的相似等。群的顶底界线一般为不整合面或明显的沉积间断面。常用于前寒武系和中生代陆相地层 段-Member：组的再分。分段的原则：组内岩性的差别；组内结构的差别；地层成因的不同等。段的顶底界线一般是标志明显的整合界线。  层-Bed：层有两种类型：一是岩性或结构相同或相近的岩层组合，可以用于剖面研究时的分层。二是岩性特殊、标志明显的岩层或矿层。 Group→ Formation →Member →Bed;岩石地层单位的级别Hierarchy of lithostratigraphic units;命 名Nomenclature of lithostratigraphic units群和组：大都以建群、建组剖面所在的地名命名,如：长城群(Pt2),融县组(D3) 段和层：大都以岩性命名, 如:砂岩段, 灰岩层.;2 生物地层单位/Biostratigraphic Units and their Main Types;生物带的主要类型(Major types of biozone);a. Taxon-range Zone;The body of fossilife-rous strata between two specified biohorizons.  Such a zone is not itself necessarily the range zone of a taxon or concurrence of taxa; it is defined and identified only on the basis of its bounding biohorizons; The body of strata containing specimens representing a specific segment of an evolutionary lineage..It may represent the entire range of a taxon within a lineage or only that part of the range of the taxon below the appearance of a descendant taxon. The boundaries of lineage zones approach the boundaries of chronostratigraphic units;The body of strata characterized by an assemblage of three or more fossil taxa that, taken together, distinguishes it in biostratigraphic character from adjacent strata. ; The body of strata in which the abundance of a particular taxon or specified group of taxa is significantly greater than is usual in the adjacent parts of the section. Unusual abundance of a taxon or taxa in the stratigraphic record may result from a number of processes that are of local extent, but may be repeated in different places at different times.For this reason, the only sure way to