塔里木盆地西南地区白垩系沉积相特征

塔西南白垩系发育,可分为上、下两统。下白垩统克孜勒苏群可分4段,多以陆相沉积为主,富含棕红色砂砾岩夹少许砂岩、粉砂岩、泥岩和砾岩。上白垩统英吉沙群为海陆相并存,库克拜组可分2段,常见泥岩、膏岩和海相化石;乌依塔格组多为红色泥岩、泥质粉砂岩夹砂岩;依格孜牙组多见灰岩、白云质灰岩,富含海相化石;吐依洛克组为棕红色泥岩、石膏和砂、砾岩,含海相化石。通过勾勒9个岩性单元的沉积相展布,分析昆仑山前白垩纪的沉积环境演化过程。克孜勒苏群西区多为陆相快速堆积,东区远离陆源为三角洲和滨岸沉积,具有宽泛的冲积扇—辫状河三角洲相分布。库克拜组总体显示为辫状河三角洲—潮坪相变的过程;乌依塔格组以潮坪为主;依格孜牙组表现为碳酸盐岩台地—台地边缘的演化;吐依洛克组为宽广潮坪。

Sedimentary facies characteristics of the Cretaceous in southwestern Tarim Basin

In southwestern Tarim Basin, the Cretaceous was developed well with Upper and Lower. The Lower Cretaceous Kizilsu Group is subdivided into four members. They are dominated by terrestrial sedimentary rocks of brownish red glutenites intercalated with sandstones,silts,mudstones and conglomerates.The Upper Cretaceous Yengisar Group is composed of both marine and non-marine facies and summarized in ascending order.The Kukebai Formation is subdivided into two members and commonly composed of mudstones, gypsum beds and marine fossils. The Wuyitage Formation is characterized of red mudstones and muddy silts intercalated with sandstones.The Yigeziya Formation is rich in limestones, dolomitic limestones and marine fossils. The Tuyiluoke Formation is composed of brownish red mudstones,gypsum beds, sandstones, conglomerates and some marine fossils.Thestudy supplies an evolutionary process of the northwestern Tarim Block during the Cretaceous based on the temporal and spatial distribution of nine units covering the fore-land region of the Kunlun Mountains. The Kizilsu Group shows rapid terrestrial deposition spped in the western part, and delta and shoal facies in the eastern part where is short of clastic supplement.It is recognized as a wide facies of alluvial fan and braided river delta. The Kukebai Formation generally implies a transgression with a facies change from braided river to tidal falt.Tidal flat facies are mainly arrangement of the Wuyitage Formation. The Yigeziya Formation showed facies changed from carbonate platform to platform margin. The Tuyiluoke Formation is a persistence of a wide tidal flat environment.