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
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摘要: 提要: 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。Abstract: Abstract: 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 bauxite-bearing 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 series in central Guizhou-southern Chongqing area was very?diverse and complex. It was affected not only by continental sedimentary environment but also by other factors.