广西合山煤田的古土壤层与成煤模式

The Paleosol Bed and the Coal Deposition Model in Heshan Coalfield,Guangxi,China

合山煤田主采煤层底板发现古土壤层，在煤分层之间又发现稳定的陆相根土层，结合煤本身的微量元素含量分析，并与现代咸水植物及现代淡水植物的微量元素含量对比，对这种夹在海相碳酸盐岩中的煤层的成因有了新的认识。作者认为，主采煤层与其间接底板碳酸盐岩间存在沉积间断；合山组含煤岩系中可见规模极小的孤立的海绵小礁块，这些都是碳酸盐台地表面浅水环境常见的特征。分析黔桂两省大面积古地理背景，作者认为，合山煤田主采煤层形成于碳酸盐台地表面废弃潮坪上发育的泥炭沼泽，少数地段则是在碳酸盐台地表面闭塞水体进一步沼泽化的条件下形成的。

The research about the following three aspects provides the evidences for that, the depositional environment when Heshan Formation sediments deposited was mainly shallow, and the carbonate platform surface was relief.1. Almost all the limestones composing Heshan coal-bearing formation are shallow-water limestones.2. Small quantity sponge-reef rocks of Heshan coal-bearing formation are provided with the characteristics of dispersed and isolated small reefs.3.There was a depositional break between No.Ⅳ coal-seam and it's indirect carbonate floor. The discovery of the paleosol,which originated from intertidal blue alage rock underwent soil weathering and siliconizing on supratidal zone, under neath the main coal-seam, and discovery of terrestria seat earth, and the contents of some microelements in the No. Ⅳ coal-seam are nearing that of plants of fresh water,demonstrates that the coal-seam in Heshan coalfield formed in the marshes arised on the abundonment carbonate tidal flat and some of them in minor region,were originated under the condition of the process of turning the closed water-body into swamps on the surface of the carbonate platform.