GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENT OF LOWER TRIASSIC HONGLA FORMATION IN SOUTHERN KAILU BASIN: A Case Study of NC1 Well

The major, trace and rare earth elements of 26 fine clastic rock samples from NC1 well are tested and analyzed to reveal the tectonic setting and sedimentary environment of Lower Triassic Hongla Formation in southern Kailu Basin. The results show that the sediment sources of Hongla Formation are diverse, mainly from the felsic rock source area in the upper crust with minors from the intermediate and basic igneous rock source areas. The tectonic setting of the provenance is mainly active continental margin, which may be formed in the tectonic background of active continental margin near the continental island arc. The Hongla Formation is generally in an oxidative-weakly reductive terrestrial freshwater-brackish water sedimentary environment, with the water salinity increasing from bottom to top. The paleoclimate was arid and hot on the whole.