准噶尔盆地南缘上三叠统黄山街组辫状河三角洲沉积

准噶尔盆地南缘上三叠统黄山街组主要为砾岩、含砾砂岩、砂岩、粉砂岩和泥岩构成的一套碎屑岩组合，野外沉积特征研究确定为典型的辫状河三角洲沉积。通过对沉积相、亚相、微相的详细研究，认为辫状河三角洲具有类似曲流河三角洲的层序结构和微相类型，但两者间也存在很大的差别。与曲流河三角洲相比，辫状河三角洲的三角洲平原亚相不仅沉积物的粒度较粗，而且辫状河道沉积较发育，河道间洪泛平原沉积不发育。辫状河三角洲前缘亚相也可以识别出水下分流河道、河口坝、席状砂和水下分流河道间等微相，水下分流河道沉积为主体。根据野外露头的追索研究，建立了准噶尔盆地南缘上三叠统黄山街组辫状河三角洲的沉积模式。从沉积物的岩性特征看，辫状河三角洲砾岩和含砾粗砂岩体具有分布较稳定、展布较广、储集物性较好的特点。

Braided river delta sediments of the Huangshanjie Formation of Upper Triassic in southern Junggar Basin

The Huangshanjie Formation of Upper Triassic in the southern Junggar Basin is mainly a set of terrigenous clastics,including conglomerates,conglomeratic sandstones,sandstones,siltstones and mudstones etc. According to the study on field outcrops,a typical braided river delta deposit was recognized.Studies on sedimentary facies,subfacies and microfacies show that the sequence structure and microfacies types developed in the braided revier delta are similar to those in the meandering river delta.Compared with the meandering river delta,the sediments of braided revier delta are coarser in size,and the sediments of the braided distributary channel in the braided delta plain are widely spread,while the sediments of the inter-braided channel are not well developed.The microfacies types of braided river delta front include the subaqueous distributary channel,mouth bar,sheet bar,and subaqueous interdistributary channel. Subaqueous distributary channel was well developed.Based on the detailed study on sedimentary characters of outcrops,the sedimentary model of the braided river delta of the Huangshanjie Formation was set up.The thickly-bedded conglomerates and conglomeratic sandstones developed in braided river delta are widely distributed,and are favorable oil and gas reservoirs.