摘要
The Olenekian Stage of the Lower Triassic is named from the Boreal Realm, but the stage has never been properly defined, nor has it been applied in the low-latitude Tethyan Realm, with exception of North Caucasus and Mangyshlak. This paper proposes a stratotype for the In-duan-Olenekian boundary in the low-latitude Tethyan Realm. South China is one of the main regions in the Tethyan Realm with well-developed Lower Triassic sequences and abundant fossils. According to the basic stratigraphic records and various accumulated data, we believe that the West Pingdingshan Section in Chaohu, Anhui Province is one of the best sequences to define the Induan-Olenekian boundary. The first appearance datum (FAD) of conodont Neospathodus waageni is the preferred index to define the boundary. This datum lies 26 cm below the FAD of the ammonoids Flemingites and Euflemingites, and is located slightly prior to the top of the second Triassic normal magnetozone, and the peak of the first Triassic positive excursion of carbon isotope σ13C.
The Olenekian Stage of the Lower Triassic is named from the Boreal Realm, but the stage has never been properly defined, nor has it been applied in the low-latitude Tethyan Realm, with exception of North Caucasus and Mangyshlak. This paper proposes a stratotype for the In-duan-Olenekian boundary in the low-latitude Tethyan Realm. South China is one of the main re-gions in the Tethyan Realm with well-developed Lower Triassic sequences and abundant fossils. According to the basic stratigraphic records and various accumulated data, we believe that the West Pingdingshan Section in Chaohu, Anhui Province is one of the best sequences to define the Induan-Olenekian boundary. The first appearance datum (FAD) of conodont Neospathodus waageni is the preferred index to define the boundary. This datum lies 26 cm below the FAD of the ammon-oids Flemingites and Euflemingites, and is located slightly prior to the top of the second Triassic normal magnetozone, and the peak of the first Triassic positive excursion of carbon isotope d 13C.
基金
the National Natural Science Foundation of China(Grant No.40072011)
the China National Commission on Stratigraphy
the Minis try of Science and Technology,and the Chinese“973 Program”(Grant No.G2000077705).
