茅口期相对海平面变化对类动物群的影响——以贵州盘县火铺镇茅口组剖面为例

IMPACT OF RELATIVE SEA LEVEL CHANGES ON THE MAOKOUAN FUSULINACEAN FAUNA IN PANXIAN, GUIZHOU

分析贵州盘县火铺镇茅口期海平面变化的过程和类动物群的变化规律 ,研究相对海平面变化对类动物群构成及演替的影响。相对海平面的升降变化可引起水深及相关生态条件的改变 ,并对类动物群产生影响。相对海平面变化的幅度和速率是造成类动物群面貌变化的重要因素。三级相对海平面上升末期和下降末期 ,海平面的大幅度抬升或下降是造成类物种丰度下降、新种增加量减少的重要原因 ,海平面的持续缓慢上升或下降有利于类物种丰度的增加和新种的出现 ,而海平面快速上升或下降则是一个不利的因素。茅口期晚期最大的一次类物种绝灭高峰可能与这一时期三级海平面上升初期的海平面快速抬升有关。十米级相对海平面变化较为频繁 ,对类背景演化有着重要的影响 ,是导致类动物群物种更替的主要原因。

The analysis of sequence stratigraphy and fusulinid assemblages from the Maokou Formation in Panxian, Guizhou Province, southwestern China, provides a framework to study the interrelated changes of relative sea level and fusulinacean fauna in the Maokouan period (middle Permian). The results of this study have demonstrated that the rate and amplitude of sea level rises and falls were important factors causing changes in the fusulinacean fauna. The decreases of species diversity and first appearance of species within the fauna might be due to the sea level changes with high rates and amplitudes. The extinction pulse of fusulinid species in the late Maokouan was attributed to an early fast rise of three grade sea level. It has also been found that ten meter grade sea level changes had an important influence on the background evolution, i.e., the normal appearance and disappearance of species, of fusulinacean foraminifers as well as on the species replacement within the fauna. The study of impact of sea level changes on fusulinacean fauna can help to understand the evolutionary process of fusulinaceans in the Maokouan and reveal the causes of the middle Permian extinction event.