Triassic Chronostratigraphy and Chinese Stages

Construction of a g1oba1 scheme of Triassic time scale was the first key task of the Subcommission on Triassic Stra- tigraphy(STS) since its foundation in1971. Based upon the scheme of Triassic time scale resulted from the research of the In- tcrnationa1 Gco1ogica1 Corrclation Programmc IGCP-4 (Triassic of thc Tcthys Rcalm) , thc STS mcmbcrs madc an in-dcpth dis- cussion and fina11y voted in1991 for the scheme that the Triassic is divided into3 series and7 stages. STS has been working on the selection of the G1oba1 Stratotype Section and Point(GSSP) of the stage boundary. However, only3 GSSPs have been de- cided in the Triassic up to the present, and among them only the base of the Triassic, i.e., the base of the Induan Stage, has been we11 studied and widely applied to various areas over the world, whereas the other2 GSSPs, i.e., the bases of the Ladinian and Carnian stages, are defined through the traditiona1 ammonoid indexes and their extension and application need to be con- firmed by further investigation. The selections on the stratotypes of the remaining4 stages have been in progress but they are cha11enged by some issues, especia11y the decision of the Induan-01enekian boundary stratotype. Considering the di価culties in the construction of the Internationa1 Chronostratigraphic Chart, the Stratigraphic Commission of China proposed a Chinese Chronostratigraphic Chart in2000 to meet the demands of the geo1ogica1 survey and researches in China. Since the Triassic was the turning period from marine to terrestria1 facies in the geo1ogica1 history and both marine and terrestria1 Triassic strata are widespread in China, two schemes of Chinese Triassic chronostratigraphic division corresponding respectively to the marine and tcrrcstria1 「acics and rclatcd Chincsc stagcs havc bccn suggcstcd. A11tcr tcn ycars o」1 study and application, thc schcmcs 」1or thc Chinese Triassic chronostratigraphic divisions and stages have been improved and refined, which promotes the standardization of the Triassic studies in China, and facilitates the g1oba1 Triassic stratigraphic and related researches as we11.