黔中-渝南石炭纪铝土矿含矿岩系中的海相沉积特征

Characteristics of marine deposits of the bauxite-bearing rock series in central Guizhou-southern Chongqing area

黔中—渝南地区于紫云运动初期的泥盆纪末已准平原化,在石炭纪铝土矿含矿岩系沉积过程中,含矿岩系下段(铁质-粘土岩段)主要为近海湖泊相,含矿岩系上段(铝质岩段)为近海平原相。在这种大环境前提下,经常会受到海泛与强风暴潮的影响与改造,使得主要是陆相环境沉积形成的铝土矿含矿岩系中,含有少量海相大化石(腕足类)和微体生物化石(疑源类和牙形石);另在下段和上段岩矿层间,时夹海相碳酸盐岩透镜体,具明显海相沉积特征。以上表明,黔中—渝南石炭系铝土矿含矿岩系形成环境具有显著的多样性和复杂性,而非单纯的陆相沉积环境所能概括的。

The central Guizhou- southern Chongqing area had experienced peneplanation at the beginning of Ziyun Movement before the end of the Devonian. In the deposition process of the Carboniferous bauxite- bearing rock series, the lower bauxitebearing rock series（iron- clay rock） was mostly offshore lake facies, and the upper bauxite- bearing rock series（aluminous rock）was mostly offshore plain facies. In this environment, the influence and reformation of ingression and strong storm surge were frequent. Thus, there exsited a few marine plant fossils（brachiopoda） and marine microfossils（acritarch and conodont） in the bauxite-bearing rock series, which mostly deposited in a continental environment. And there were less marine carbonate lens in the lower（iron- clay rock segment） and the upper（aluminiferous rock segment） bauxite- bearing rock series, suggesting obvious characteristics of marine deposition. All these phenomena indicate that the formation environment of the bauxite-bearing rock seriesin central Guizhou- southern Chongqing area was very diverse and complex. It was affected not only by continental sedimentary environment but also by other factors.