广西南丹泥盆纪缺氧盆地沉积模式及其演化

根据Rhoads-Morse-Byers缺氧盆地生物相模式.同时考虑水体深度,将缺氧盆地沉积自上而下划分为充氧带、弱氧带和无氧带,与之相应的生物带则为喜氧生物带、贫氧生物带和厌氧生物带,按照这种模式,着重描述了广西南丹泥盆纪缺氧盆地的沉积特征及生物群特征。其演化大致经历了（1）充氧沉积-喜氧生物群阶段（D₁1）;（2）弱氧沉积-贫氧生物群阶段（D₁2-D₂）;（3）无氧沉积-厌氧生物群阶段（D₃1）;（4）弱氧沉积-贫氧生物群阶段（D₃2）。

Sedimentary Model and Evolution of Devonian "Nandan Anoxic Basin" in Guangxi Province

Based on Rhoads-Morse-Byers Model of biofacies in an anoxic basin with consideration of the depth of water, the anoxic basin deposits can be downwards divided into oxygen-rich zone (oxygenate zone), oxygen-weak zone and oxygen-free zone. Corresponded with them are the three biozones as aerobic zone, dysaerobic zone and anaerobic zone. According to the model, this paper deals with the characteristics of the Devonian deposits and biotas in Nandan, Guangxi Province. The Devonian deposits in this region are supposed to be the anoxic basin rocks accummulated in a rifted trough environment. As the result of the increase of separating of earth crust in the end of Early Devonian, the oxygen-weak deposits were presented at Luofu, the central zone of the basin, and lasted into Middle Devonian. At the margin of the basin, such as in Mangchang, delta deposit were occurred in Nabiao age (D₂1) At the begining of Late Devonian, the oxygen-free sediments with volcanic tuff were deposited in the basin, then the basin began to inversion in the late stage. Summarily, there are four stages that can be divided during the evolution of Devonian sediments and biotas in Nandan anoxic basin: (1) oxygen-rich (oxygenate)-aerobic (D₁1), (2)oxygen-weak-dysaerobic (D₁2D₂), (3)oxygen-free naerobic (D₃1), and (4) oxygen-weak -Hiysaerobic(D₃2).