摘要
四川广元上寺剖面是我国著名的二叠系-三叠系界线剖面之一,李子舜等(1986)和杨遵仪等(1987)曾推荐它为国际二叠系-三叠系界线候选层型剖面。60年代初中国科学院南京地质古生物研究所川北地层队率先对这个剖面的二叠系和三叠系进行调查。此后,四川二区测队、西南地质研究所、四川石油管理局、武汉地质学院、成都地质学院等均先后到此作了大量工作。70年代末杨遵仪教授组织的界线专题小组(IGCP 106项和
Where is the exact position of P/T boundary in the Shangsi section? We think the boundary position must coincide with the definition of P/T boundary. After the Moscow meeting of PTWG in 1984, most WG members agreed to use the traditional boundary.i. e. the base of Otoccras beds as the base of the Triassic. However, recent studies of the P/T boundary show that the known distribution of Otoccras is restricted geographically and has not yet been found in most parts of the Tethyan Realm. In its stead there appeared Hypophiceras and/or Hindeodus parvus (Kozur et Pjatakova). Thus it is imperative to supplement and revise the definition of the traditional boundary The revised definition of the traditional P/T boundary can be summarized as follows: an international P/T boundary should be selected at the base of Otoccras beds, while in most parts of the Tethyan Realm, the more widely distributed taxa Hypo-phiceras and Hindeodus parvus (Kozur et Pjatakova) can be utilized, as auxiliary species for recognition of that boundary. The basal boundaries of Otoceras beds, Hypophiceras zone and Hindeodus parvus zone can be considered to be approximately on the same isochronous level. According to the first occurrence of Hypophiceras, we place the P/T boundary between the Units 14 and 15 in the Shangsi section, which is the highest boundary position in the proposals. It is clear that this boundary position coincides with the revised definition of traditional boundary and is the exact position of P/T boundary in this section.
出处
《地层学杂志》
CSCD
北大核心
1989年第2期151-155,143,共6页
Journal of Stratigraphy
基金
国家自然科学基金
