The formation and evolution of the Jiama intra-arc basin in Xizang

The Jiama intra-arc basin located in the Gang dise tectonic belt, Xizang was formed with the development of the Jiama island arc, where there occurs a succession of littoral and shallow-marine active marginal sediments consisting of clasticrocks and sponge-reef limestones. The Upper Jurassic and Cretaceous strata in the basin may be grouped into seven third-o rder sequences including one type 1 sequence and six type 2 sequences.The stratigraphic framework has been reconstructed for the basin.The study of sequence stratigraphy indicates that the basin has experienced five stages of evolution:(1) deeply incised siliciclastic shelf;(2) carbonate platform and sponge reefs;(3) stagnant siliciclastic shelf; (4) non-barrier siliciclastic shelf, and (5) barrier siliciclastic shelf.