The extremely gentle slope of the large coal-accumulating basins in the Late Palaeozoic epicontinental seas in North China is believed to be good sites of coal accumulation.

• 华北晚古生代内陆表海大型聚煤盆地的极平坦的地势是煤聚积的良好场所，而事件性海侵为泥岩沼泽发育及泥炭迅速得以保存最终形成煤层提供了条件。