The main controlling factor of the distribution and mutual replacement of the brachiopod communities is relative sea-level change. 控制腕足动物群落分布和相互取代的最主要因素是相对海平面变化。
There were three sea-level change cycles during Xishanbulake stage.The phosphorite was the result of the earlier sea-level change. 西山布拉克组沉积时期经历了三次海平面的升降变化，磷质岩是早期海平面变化的产物。
