合山煤田煤层的成因问题一直存有争议。通过露头层序地层分析将该区煤层分为两种类型，一种产在台地低水位楔状体内，另一种产在海进体系域中。前者厚度大，结构较简单，煤质较好，为近海湖泊淤浅成煤；后者厚度小，结构复杂，煤质差，为滨海潮上带成煤。其独特的碳酸盐岩型含煤是由于缺乏陆源碎屑供应等所致。 Hushan coal seam causes of the problem has been controversial. By outcrop sequence stratigraphic analysis, the coal seams are divided into two types, one in the low water level wedge of the platform and the other in the marine system tract. The former has a large thickness, a simple structure and a good coal quality, which are shallow silt into the sea near the lakes. The latter is small in thickness and complicated in structure, and has poor coal quality and is coal in the coastal tidal zone. Its unique carbonate-type coal is due to the lack of terrestrial debris supply and so on.