汝箕沟盆地上三叠统延长组沉积环境

Sedimentary environment of Yanchang formation of the Upper Triassic in Ruqigou basin

认为汝箕沟盆地上三叠统延长组具有 3套岩性组合 ,在古气候及构造运动共同影响下 ,形成了冲积扇、辫状河、辫状河三角洲和湖泊沉积体系。其中辩状河以发育的河道砂坝为特征 ,辫状河三角洲河口坝不发育 ,剖面上水下分流河道频繁交替 ,并首次在本区发现深湖相浊积岩。

Based on studying carefully sedimentary environment of Yanchang formation of the Upper Triassic series in Ruqigou basin, in the stratum there are three group lithology assemblage which form sedimentary systems of alluvial fan, braided stream, braided delta and lake by influencing paleoclimate and tectonic movement. The sandbodies of braided stream is very thick and the scope of the sandbodies is widespread. In deep lake, tarbidite which is found for the first time is developed and mainly consists of four stratigraphic sequences which include ABE, AE, BCDE and CDE styles sequences. From early period to late period of Upper Triassic, climate had evolved from semiarid to moist. The basin had sunk rapidly in early phase of Upper Triassic and the basin became slowly stable in the phase.