敦煌盆地东部侏罗纪原型盆地探讨

Study on Jurassic Prototype of the Eastern Dunhuang Basin

摘要: 以敦煌盆地东部各凹陷为研究对象，系统分析了侏罗纪盆地构造格架及沉积充填特征，恢复了其原型盆地。研究结果表明：侏罗纪之前，敦煌盆地与周边盆地具有相似的演化背景，至三叠纪末期，盆地“三山夹两坳”的构造背景初步形成；早侏罗世，敦煌盆地发生断陷，形成一系列彼此分割的小型凹陷，发育冲积扇–辫状河–湖沼相粗碎屑沉积；中侏罗世，湖盆范围进一步扩大，五墩凹陷发育半深湖–深湖相沉积，中–下侏罗统最大沉积厚度为1100 m，其他凹陷中–下侏罗统最大沉积厚度为600 m，以滨浅湖沉积为主；晚侏罗世时期，盆地发生整体拗陷，普遍接受上侏罗统沉积，充填了棕红色河流相砂砾岩沉积物。

Abstract: The Jurassic prototype of the Eastern Dunhuang Basin was studied from tectonic framework and sedimentary filling characteristics, and the prototype of the basin was restored. The results showed that evolution characteristics of Dunhuang Basin were similar to adjacent basins before Jurassic. The tectonic framework of “two depressions between three hills” was formed in the end of the Triassic. Dunhuang Basin was down faulted and formed a series of small sags in early Jurassic, which were separated from each other and filled with coarse clastic sediments of alluvial fan-braided river-limnetic facies. In the middle Jurassic, the lake basin spread more widely. In Wudun Sag, half-deep lake and deep lake facies were developed and maximum thickness of the Middle-Lower Jurassic strata was 1100 m. In contrast, in other sags shore shallow lake sedimentation system was mainly developed and maximum thickness of the Middle-Lower Jurassic strata was about 600 m. In late Jurassic, the Dunhuang Basin integrally sagged and was universally filled with brown-red sandy conglomerate of fluvial facies.