大别造山带北缘早白垩世周公山组冲积沉积研究

发育于安徽肥西—六安一带的周公山组,属于早白垩世沉积,厚度大于800 m。周公山组以不等粒砂岩和泥岩、粉砂岩为主,局部含砾岩。根据Miall的岩相分类,周公山组有12种岩相,主要为Gci、Gcm、Ss、Sp、Sh、Sm、Fsm和Fm等。识别出6种沉积结构单元,分别是河道滞流沉积、曲流砂坝、天然堤、决口扇和洪泛平原沉积,其中决口扇和洪泛平原沉积是最为发育的结构单元。根据Miall的河流分类方案,肥西周公山组下段应属于细粒曲流河沉积,上段属于砂质曲流河沉积。河流曲率P为2.09~3.55,河道宽度31.4~81.1 m,河流曲率波长为385.63~1025.66 m。周公山组沉积环境的变化可能记录着物源区—大别造山带隆升速率的变化。

Study on alluvial sediments of Early Cretaceous Zhougongshan Formation in the northern margin of the Dabie orogenic belt

The Early Cretaceous Zhougongshan Formation(ZgsF.),which developed in the Feixi-Lu'an region,Anhui Province and is above 800 meters thick,comprises mainly fine-to coarse-grained sandstone,mudstone and siltstone,and a little conglomerate.According to Miall's facies classification,it consists of twelve kinds of facies,and the main facies are Gci,Gcm,Ss,St,Sp,Sh,Sm,Fsm and Fm. Six architectural elements such as channel lag deposit,meander sandy bars,levees,crevasse splay and floodplain fine are distinguished,among which crevasse splay and floodplain fine are most abundant.According to stream features of 16 kinds proposed by Miall,it is believed that the lower member of ZgsF.belongs to sediment of fine-grained meandering streams and the upper member corresponds to that of sandy meandering streams.The channel sinuosity(P) is 2.09 ~ 3.55.The channel is 31.4 ~ 81.1 meters wide.The channel meander wavelength is 385.63 ~1 025.66 meters.The change of sedimentary environment of ZgsF.might record the difference of uplift speed of the provenance,the Dabie orogenic belt.