APPLICATIONS OF SEDBA TO THE TRIASSIC STRATA IN LONGMENDONG,MT.EMEI,SICHUAN,CHINA

Applications of the geochemical data in the SEDBA of the Triassic in the Longmendong section,Mt. Emei to chemical strata and to sea-level Changes and sequence stratigraphy are pre-sented in the paper. The division of the chemical unit sets accords fully with the boundary Of the lithostratigraphic groups,Some of chemical units are different from the division of lithos-tratigraphic members. Many of chemical units accord with the depositional system tracts. Three depositional and shallow buried diagenetic environments of the carbonates are divided based on the regional clustering features in the scatter diagram of the distribution of the δ¹⁸O and δ¹³C of carbonates;combined with thin-section identification. Deposition of T₁j¹ and T₁j³ members occurred in normal saline environment,majority of other lithostratigraphic members deposit in hypersaline environment. There are the cyclic changes in the vertical curve change of δ¹⁸O and δ¹³c. The δ¹⁸O values of fine and denes carbonate rocks without alteration possess the corresponding cyclic variations related to the depositional environments. The δ¹⁸O as a geo-chemical responses to the sea-level change or eustacy,provides the criterion for the relationship of global sea-level Change and the rate of regional tectonic subsidence and the rate of clastic ma-terial supply. It is believed that marine transgressions in T₁j³ and T₂l³ member are due to global sea-level rising;meanwhile,the smaller transgression or relative sea-level rising is ralated to the larger rate of regional tectonic subsidence than the rate of clastic material supply and carbonate Production,and the rhythmic interbeds consisting of sandstones and limestone beds are also due to the frequent variations in the preceding two rates. Besides,the origin of the rocks in some members and beds,and properties of some boundary lines or interfaces have been briefly ex-pounded in the paper.