| The Guan Ziba section is located in Wangcang County, Guangyuan City,northern margin of the Sichuan Basin, China. The Lower Triassic System is wellexposed at the Guan Ziba section with the quite thicker sediment. And the sectioncontains a lot of important Lower Triassic conodont species, and it is one of thesections which involve complete Lower Triassic sediment in the Sichuan Basin.Conodont biostratigraphy is utilized as the primary approach to study the LowerTriassic sediment of the section. Many samples were collected systematically fromlimestone layers of the section. Then, the careful handling and accurate identificationof the conodont was made. The extracted200conodont elements include18stratigraphically significant species referable to9genera: Ellisonia, Furnishius,Neogondolella, Hindeodus, Isarcicella, Parachirognathus, Pachycladina, Hadrodon-tina and Neospathodus. Three conodont zones of the Lower Triassic had beendistinguished. In ascending order, they are: Isarcicella isarcica zone, Parachi-rognathus delicatulus-Pachycladina obliqua zone, Neospathodus triangularis zone.They may be precisely correlated with contemporaneous ones in the Pingguo(Guangxi Province), Chaohu (Anhui Province), China and Southern Alps of Italyand also with the Lower Triassic conodont sequences from different facies in Chinaand of international standard. The age of each zone was determined and respectivelybelonged to early Griesbachian, Smitian and Spathian. Smitian-Spathian Boudarywas discussed and defined by the first occurrence of Neospathodus triangulariswhich was placed at2m above the boundary between the Bed121and the Bed122.The relationship of the genera in Ellisoniidae was also discussed and Hadrodontina,Pachycladina, Furnishius and Parachirognathus may be all evolved from Ellisonia.The last one started from Dienerian and the others started from early Smitian. Thesedata are evidence for erecting the Lower Triassic biostratigraphy sequence ofSichuan Basin. |
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